My tip is to play some Daily Tournament to earn some more clintz, 50k is not much
there are many good clans in elo, just find a clan you like and start to invest in buying some of those characters
just pick any deck and give it a go
You need more than that for a playable deck to be honest.
Your deck budget should be between 150k-300k depending on the clan you choose.
You should definitely start with DT's. The prizes are insane. You should have more than enough after participating in 10 of them if not less depending on where you place.
If you are creative you can make a great deck with common and uncommon cards. Usually the most expensive common cards will cost you 3000 clintz max. I used a Sentinel deck when I first started winning a lot. They are great at team damage, and Tobie is also excellent.