Where can i find a Emulator ( that works at least 90% sure ) for GameCube. And what about Roms?

if by "that works at least 90% sure" you mean fast games playable to the end, you'll find those kind of emulators nowhere. Well, ok, the only game that is fully playable seems to be Bust-A-Move 3000. Dolphin is currently the most compatible. Unless you have a dual core system and a 64-bit operating system, you won't get speeds faster than ~10fps in game.

Next, what about ROMs? GameCube's ripped games that float on the Internet are disc images. Don't you dare ask where to get those.

You need to wait for Gekko, the upcoming Gamecube emulator.

Dolphin is currently the best Gamecube / Wii emulator you can find. Gekko still needs a lot of catch up in the graphics emulation . I believe it doesn't support any Destination Alpha Blending, or Alpha Comparing, (I can't remember), I would have to ask Shizzy again.