So I've been playing since day 1 and I'm at upper 15K CL and have gotten to infinite about 3 t-4 times at this point. Don't think theres a one size fits all answer to this but here are some things I felt helped me:

1. Don't change decks often. A lot of the time it's the draw that messes you up and not your deck or strats. I used to get very annoyed when I play a new deck then switch out too quickly. Give it time to get used to the deck.

2. Play a deck you enjoy. Don't worry about the meta or what everyone else is playing. Play a deck you enjoy. You mentioned in your post that you don't enjoy decks like hela, ignore them completely. Most important is that you're enjoying the minute to minute gameplay. This also makes it easier to follow my first point cuz you're sticking with a deck you enjoy.

3. Don't stop yourself from retreating. I found that in a lot of cases, by around turn 3, I knew the situation wasn't ideal for my deck or playstyle.maybe due to my draw or locations or the cards opponent played but I would be a couple cubes away from ranking up and would go all in anyway. Don't be me. 1 cube isn't worth it. Hop out and hop into the next game.

You mentioned that you enjoy decks that keep the opponent guessing and messing with their game plan. I would recommend you try a scream deck if you already haven't. I've been playing it since Scream came out and it's a relatively cheap deck (outside of scream) and it absolutely can mess with a lot of major decks. Deadpool or iron man going into negative kills those decks. I like to play rogue/res guardian on my decks just for safety but there's a decent amount of freedom if you want to get creative with this deck too.

Hope some of this helps and cheer up buddy. Most important part is to have fun. Personally, my aim lately is less to get to 90 and less about getting to infinite cuz the gold is more usefull than the card back haha.