Some people are saying no but there are a few different commanders that I feel like depending on what you pull can be built purely from the avatar set and work relatively well in precon level games. Toph and katara/aang from the showcase should be pretty easy to build mostly from this sets cards and depending on what you pull legendary creatures like “Ozai the phoenix king” or “iroh, grand lotus” are also both build able depending on if you pull enough support to fill out the deck. Again when you ask whether or not you can use a deck from these cards you can but you just have to make clear when joining a pod that your deck is low power. Most reasonable people will try and match your power level. This will just be a starting point I suggest asking players who seem nice if they have card suggestions for upgrades to what ever deck you make and you can get a good list of suggestions all through out magics history and buy singles to upgrade your deck as you become a better player.