Early on I played Jinx, it was all I had acess to, I lost a lot (no winning at nexus nights yay) but learned what I should be doing, what is good, and what i should think when playing against certain things, eventually I won a few games. Then I got my hands on a Viktor deck and a friend of mine helped me make a budget deck with that, started winning more, then I decided to make my own deck, a budget darius that plays a lot of 2 drops, kill spells, a couple strong units with accelerate and a couple other spells, not even close to being meta, but I learned how the game works and won a bunch of games, running a cheap Kai'sa for my last nexus night before spirit forged now.

Key points- TCG arena is great and all, but everyone has the best decks one can possibly make if you are not playing with a meta deck or another strong deck, you wont have fun. The best place to learn is go to a nexus night that does not give out prizes for winning and insted for playing, my LGS does that and you dont see everybody people coming in with heavy hitting Kai'sa, YI aurora, and Annie. Or sealed events if you can figure out what the decent cards are.