you need to focus getting chanpions to 60.
Its probably still worth to take kael to 60 as you can use him as a campaign farmer for a long time and being rare he will be easy to fully max out.
After that I would bring artak to 60.
Stop investing in every champion you get and focus on one at a time that will have a impact on your account.
Judging by you stats you need to also watch some videos about how to properly gear champions. There are plenty of good YouTube creators but I would suggest watching hellhades, specifically one of his free to play video series as it will take you through early game strategies to optimize your account fast.
Haha... I've been secretly watching this post to see if I could gleam a secret for my team. Didn't realize the poor chap was so low. I'm stuck at level 20. The team I have beats 20 about 90% of the time. Step up to 21 and get squished every time.
Good luck to you bud. It's a long hard road ahead of you.
To add to what evilized said:
I'd definitely hold off on bothering with Sand Devil for a while. You need to get a team of 60s together. Get a campaign farmer to 60 and then make more 60s so you can farm Dragon for gear.
As well, you can certainly stop bringing up rares like Warpriest and Spirithost, they're not worth the investment. There are very few champs below Epic worth 60ing and those are very, very limited - and sometimes not very usable early.