Basic strategy in FMA-TCG is simple - stay alive, win battles, win locations. You can do this by making the most of your allies, not playing cards when you don't need to, not getting your allies defeated, and saving up your power for when you need it. To wit, there are a few points you should always keep in mind - this doesn't mean you should always follow these religiously, but if you break one of them, you should make sure that you have a good reason why:
- First, use a 60-card deck. The smaller the deck, the less randomness, and the more you can control how you play. 65 is considered to be the absolute maximum upper limit in FMA.
- Next: 26 Allies in a 60 card deck means you draw one ally a turn for eight turns. This is a Good Thing. Maybe a little more if you play Rebel (you need more people), maybe less if you play Elric (because you survive more), but you should be sure you actually have characters to use throughout your game.
- The majority of your game will be played at Level 2, sort your allies accordingly. Say to yourself, "how many turns should I win in?" and then pick allies that fit your leader's Command. If you win in eight turns, you will spend two at Level 1, four at Level 2, and two at Level 3. Have the same ratio of Allies.
- That being said, in a deck built for one-on-one, lay off the Level Three Allies. Personally, I'd go for no more than four total cards in the deck that you must wait for Level 3 to play - otherwise, they'll just rot in your hand when you would really rather have something else.
- Make sure you can win your own locations. A Homunculus deck can beat people down at a Wits Battle, but not be able to get that Alchemy Goal. Don't play things you can't take.
- Attachments can be destroyed. If your deck revolves around your attachments, either have a way to get them back, or play the cancels you have to, because Oops, Aflame, and the Prison Guards are in play everywhere.
- Surprising your opponent can win you the game. Only let them see your hand (More, Shou's level 2, etc.) if it doesn't hurt you. A Rally the People can mean the game, as can a couple Stone Walls - don't let them prepare. That being said, showing your opponent a hand with no 'tricks' in it is the worst thing you can do.
- Cancels are only good if you've nothing better to do. Don't worry about cancelling Frenzy - you can do that by playing one of your own. If you pack 'a full set of cancels', you AREN'T packing nasty stuff to use on your opponent, and they'll realize that. Sometimes, people don't need cards to beat you - stats will do just fine.
- Don't play a card if you don't have to. Why play a +2 Strength pump from your hand when you have an unused+2 Strength from, say, Liza Hawkeye? Every card you don't play is a card you can use later, but every Ability you don't use is an Ability lost that turn.
- Realize when you are building for the meta. Just because your friend plays nothing but MM doesn't mean that three Daring Gambits and Inspectors is a good idea. Realize the difference between a good deck and a 'great' deck (that you only play against one person).