^ It's a bit more complicated than that. It's the Pokemon that make the decks, not the types. What you need to do is find Pokemon the combo well together, throw in a bunch of trainers, and throw in some energies so they can do something. Some good combos include:
Blissey MT + Delcatty PK/ Bronzong MT (Solo Blissey deck.)
Feraligatr MT + Smeargle SW + Delcatty PK + Magneton PK (Hurricane- I currently run this.)
Gardevoir SW + Gardevoir Lv.X + Gallade (Gardellade- this thing is more common than a Bidoof on Route 201. Very effective, though.)
Empoleon DP + Lucario DP (Empcario- works fairly well.)
Infernape DP + Delcatty PK + Delcatty ex PK (Infercatty.)
Weezing GE + Toxicroak MT (Toxic stall deck. I want to run this.)
Porygon-Z GE + Lake Boundary (Lake Boundary is a Stadium, but it's part of the combo nonetheless. I want to run this, too.)
Supporters form the backbone of a deck, and can help you get what you really need. Pack a good amount of these.
Professor Oak's Visit
Bebe's Search
Celio's Network
Professor Rowan
Roseanne's Research
Team Galactic's Mars
Team Galactic's Wager
Copycat
And lastly, energies. About 1/4 of the deck should be energies- pack energies proportionate to the Pokemon that use them. For example, if your Pokemon line looked like this:
2 (Random Psychic Pokemon)
3-3 (Random Grass Pokemon)
Pack more Grass energies than Psychic.
And that's all advice I can give, I think.
