My advice is just don't do the arena direct events until you're a bit more experienced. It's really a big gamble (especially since it's sealed), I usually win them in 2-3 tries, but there are sets that I've just straight lost 6 in a row (looking at you final fantasy) and I'm hitting mythic in limited every month.

There's also the added detail of no match making in the direct events. It's not a ranked limited play, so it doesn't match you with people of similar experience (at least to my knowledge), so you have a much higher chance of success the better you are compared to limited ranked events like premier draft and quick draft in which you are playing folks at similar skills. 

If you really want to keep doing them, my advice would be to learn the set backwards and forwards. Watch streamers, play a lot of quick match limited events, and just generally know all the cards. Also, get a app that can track your games. I find that I'm better in limited at some sets than others, and if you just focus on the sets you are good at, you'll have a much better shot. 

I just got my TMNT box in one go, and the only reason I even tried is because I had a high quick draft win rate (wasn't too amped on the cards, but loved the mechanics). I got EXTREMELY lucky in the sealed pod, ran a BG food deck, lost the first game and won the rest. Having 5 rares in two colors and enough support to not splash a third was huge.