Nothing can be more dangerous than a good gacha game. Because the temptation to spend money on those games is real. Dokkan Battle is the game that I've been playing real hard for a few months now. Lately with the Super Vegito banner I have been grinding so hard that I literally am exhausted from playing a game on my phone.
For my efforts I have been rewarded with some of the best cards in the game and I got the chance to make them even stronger with a bit more mission grinding.
I have both the Global and Japanese versions of the game on my phone, but since I got some sweet cards on Global I have made that account my priority and my Japanese account has taken a backseat. The Japanese version of the game has better events, but I have the better cards on Global soooo I am playing Global mainly now.
How you get cards is all RNG (Random Number Generator) and the odds of you getting the card or cards you want is absolute garbage sometimes. Paying for the stones when there is a sale to summon characters can solve some of the issues regarding how random the character drops are, but that is something for each player to decide. Paying for stones doesn't guarantee you will get the cards you want but it will allow you to get as many stones as you want and therefore you'll have much better chances to get almost any card on a given banner.
But it still not a 100% thing. You could spend thirty bucks on 90 summon stones and get jack when you try to summon. So be cautious if buying.
The following is the list of my ten favorite cards in the game that I actually have and can use at any time. If I haven't pulled it I won't list it. If I've used it in as a friend on a team it won't count unless I actually have it in my collection. Otherwise this list would pretty much all be god leader cards even though I only have one between my JP and Global account.
In case you don't know each card has certain abilities. Six cards can go on a team with the addition of a "friend" card that can be added for each mission. How these cards link together is very, very important. Leader skills are vital and support skills are vital. A bunch of SSR cards on a team means jack if they cannot support each other. So plan your team carefully.
Some cards are nukers (basically for each ki orb they streak their attack goes up a percentage), some are tanks (the ones that can take a hit), and many others have a variety of abilities that can come in clutch during a long battle. It's really important to know all passive skills, links, leader skills, and type advantages before putting a team together before going into a tough event if you want to be successful.
Some tough events will provide medals that will awaken (or evolve) your cards into something better. So when I mention that cards are or are not awakened that is what I mean.
That being said, let our list begin!
1) Super Vegito - It is quite ironic that I pulled this card for my first time ever on my Global account. He's my only god leader, but I do not have him awakened to his full potential yet and I won't be able to awaken him for a few months. He cannot tank a super attack worth a damn so a super attack sealer like PHY Gotenks is very important, but his defense against normal attacks and his subsequent counter attacks are freaking legit. As a leader he is only really good if you are running an all agility team. He can link well on a rainbow team if you have other fused saiyan cards, but he is best utilized on an all agility squad for his leader skills. My JP account has a really good agility squad but no Super Vegito and my Global account has a shit agility squad but a Super Vegito. At least I got him, I guess. Until I can awaken him I will use him as support on my Gogeta squad because his counters are really freaking sweet and he has good links. You can't not use this card if you have him.

2) Super Gogeta - I pulled him just before I pulled Super Vegito and he is an absolute beast. I managed to fully awaken him and with a double Gogeta lead all of my cards get super attacks and that is a great thing to have. That is not to say he is perfect, though. He doesn't have the health of a Super Vegito team and he has no counters. He also cannot take a hit worth a damn. But he is the second best card on Global right now next to Super Vegito. The damage he deals out was the reason I could stand a chance against Super Vegito in the boss fight. In fact, he can make pretty much any event a lot easier. He is really good as a leader for those of you that don't have any god cards (or at least haven't awakened them yet). Now if I can only pull him on JP....

3) SSGSS Kaioken Goku - This card is a boss. He does have a ten turn limitation on his passive skill so longer boss fights can be a bitch, but he is an excellent support unit on either a rainbow team or an agility squad. His super attacks (especially before the ten turns are up) are beautiful and he has great links. I do not have mine awakened yet because I don't quite have a good enough team on JP to take the event on yet. Those 77 medals will be a bitch to grind. Still, he is a glorious card without being fully awakened.

4) PHY Gotenks - This card has been with me for so long. He is my ultimate support unit on Global. The damage he deals out is decent (could be better), but his super seals and now that I have Super Vegito my life is going to be a lot easier. This card is almost guaranteed to super on a double Gogeta team and on a team with other fused fighters. The super attack seals should be happening like regular clockwork if you build your team right. Then you just let Super Vegito go to town with the counters. Easy way to take down bosses. He is not an agility card so that is a drawback for a Super Vegito squad, but JP has Oceanus as an agility sealer and he will eventually come to Global. Until that time it is vital to have a sealer like Gotenks. As a leader he isn't bad either if you don't have Gogeta or Vegito.

5) Majin Vegeta - Once you awaken this card the world tournament becomes a goddamn cakewalk. Once this card supers he attacks every other card on the field. He might not destroy everyone depending on their health, but he will make a fight against multiple characters so much easier. Unlike STR Broly he does not have shit links so he is almost always going to have a super ready to go if you build a decent team around him. I wouldn't have him as a leader, but that AOE super is gorgeous so he is a must have on a WT team.

6) AGL Golden Frieza - I have way more defensive powered cards on my JP account than my Global account. My favorite (for the moment) is this glorious bastard. He can tank those supers easily and he would be great support on a Super Vegito team. When you cannot seal then you need to tank and that is when you use this guy. Unfortunately I don't have him on global and I don't have Vegito on JP so... I kinda feel unfulfilled. I've got two cool accounts that are growing, but if I could combine them I'd have it made. But I can't so I just got to tank my hits until I can get my Super Vegito on JP. And I have to go without a tank on Global and use all my items up to reduce damage. How depressing. This card makes life in Dokkan Battle a bit easier for the AGL squad. Or any squad. Just be careful with his passive. If you go below 50% health he will not tank a hit.

7) Great Ape Turles - Speaking of the AGL squad, we've got our resident wild card Turles. Not only does he have the chance to become a great ape and dish out some serious damage (during which time he is invulnerable), but he can also stun the enemy. Neither I would count on during a serious battle because it's always random, but it is sweet when it happens. As a leader he is decent and provides a ki and attack boost to all types. He is sort of like a poor man's Gogeta, I think. His links could be better, but villains always get the shaft in this game. He has the "Prepared for Battle" link, though.

8) Super Saiyan God Goku - I am lucky enough to have this card on both accounts. He's easily one of the strongest cards that doesn't have a Dokkan Awaken. There are better cards than him in the game, but he has three key links that put him over many: Shocking Speed, Prepared for Battle, and Over in a Flash. I would not put him as a leader, but he is really good support on my Gogeta-led team on Global.
9) Janemba - I got this guy twice on JP. He's a tank and his supers lower the defense of the enemy. He has the Shocking Speed link that gives ki and he gets the Fierce Battle when he gets awakened. So if you need to wear down some defense and take a hit then this is your card. He's just hard to give a super attack to because his links aren't so good. Frieza's links weren't good either, but Frieza makes up for by being a nuker.
10) INT Piccolo - Here we have another tank on JP. If you joined the recent tournament and made any kind of effort you got this guy in your inbox. He is a free tank and he has an awakening that will turn him into an even bigger tank. I have this guy, Janemba, and Golden Frieza on my team so I can take pretty much any hit. It really is nice. He can't link, but his passive is sweet.