Alright, me and my friend URYU have figured out some possible cheats about this game. Actually, I would call it cheating, but I wasn't sure if everyone else would think that. I myself, have some strategy for you all, and I'm willing to share all of this.
First of all, here's some cheats (possibly)
The Tournament Cheat
Ok, you all should know that after you beat story mode you have to get characters from tournaments and dragon balls, ok? Well, for the tournaments, I'll tell you which tournament and difficulty of the tournament you have to do.
Spopovich: Beat World Tournament
LEVEL 3
Pilaf's Machine: Beat Wourld Martial Arts Big Tournament
LEVEL 2
Cyborg Tao: Beat Other World Tournament
LEVEL 2
Fasha: Beat Yamcha Games
LEVEL 3
King Cold: Beat Cell Games
LEVEL 3 (Hardest one IMO)
Now, that's pretty straight forward. U will only get to play a single tournament about 2 or 3 times? (can't remember which) And you will notice each time you play a tourney the time will go by.
Now, here's the trick:
Say you already unlocked Spopovich, but u still can't do the World Martial Arts Big Tournament. Now you can do these 2 ways; You can either play the tournaments till the time passes, OR simply go into the part where u have to select the tourney, hit b to the main menu, then go back in. If done correctly, you will have noticed that the time changed, and a new tournament may be open. You can use this cheat to get to whatever tourney u need, and if say Yamcha Games is at level 1, rather then level 3, then u'll have to use the time cheat to go back. Each time you play a tourney it will be a different level.
The Dragonball Cheat
Well, this isn't really a cheat, but I know some people will need this to unlock the 2 characters Future Gohan, and Kid Chi-Chi. What you simply have to do, is keep playing easy levels such as Lord Slug, and keep ramming through the buildings till you get the dragonball. Simply win ur fight after this, and ur done.
NOTE: You can only get it from 1 level 3-4 times, then it will not give u any more.
You should also know that after you get the all the dragon balls, you will be able to call one of 3 dragons. Here's what each of them do:
Porunga:
3 Wishes, Get items.
Shenron:
1 Wish, Get Future Gohan, Strages
Red Shenron:
1 Wish, Get Kid Chi-Chi, Stages
Now for the trick. Whenever you get the dragon, if it isn't the one you want, simply reset (or turn off and turn back on) ur
Wii, then go to the dragon again. Sometimes you'll get the same one, but trust me, THIS DOES WORK. This helped me get Shenron and not that dumb Porunga all the time >_>
NOTE: You MUST have saved after you got ur last dragon ball for this to work.
Ok, I think that's all the cheats I know so far. If I find anymore, I will update. Hope they help you out!
__________________________________________________ _______________
Strategy
Ok, I will now give u strategy coming directly from me. Strategies on certain levels may be requested, but for now I will only give strategies for fighting.
NOTE: This guide is made for the GAMECUBE CONTROLLER. That is the best controller to use it in, so if ur not using it, USE IT! It's not impossible to use this without the GC Controller, but it is recommended.
MAX POWER Mode
Max Power Mode. You all know this as the thing that lets you use your Ultimate Attack. But, there are also many other uses for it.
Effective Comboing:
If you have gone through all the ultimate training, then you should already know this. When in Max Power mode, you can do a combo where you hold A up, and they will hit them high up (this is unblockable in Max Power Mode) then, you can push the Y button (or whatever button lets you use vanishing combos) then push B button (or whatever button you use to rush after ur opponent) after and you will rush after them, then press A again to hit them up in the sky like u did before, then Y, then B and A, then Y again, and you should use something similiar to ur standard special instead of just hitting them. This is a very effective combo and if used right can take of massive amounts of damage. The way I use it, after I hit them towards the ground with the last Y, I use my Ultimate Attack on them
Freely Teleporting:
First off, I bet most of u don't even know this. When in Max Power Mode, certain characters (I have a list, but I'm 2 lazy to get :P) can freely teleport. To use, simply go in a direction and push Y (or the button u use for vanishing attacks) and they should teleport in whatever direction you chose. Freely teleporting can be effective, You can use it to break through buildings, dodge attacks, and easily get to ur opponent if done repeatidly.
NOTE: This drains your Max Power Mode rather quickly, only use if u need to.
__________________________________________________ _______________
So far, that's the only Strategy I can think of off the top of my head. I will update when I remember/get more. Remember, if you have a certain level you need help with, you can always request it. Hope this guide helps!