I'd suggest you start with Montana deck since you already have quite a lot of those cards.
Seeing as you bought credits, you could sell cards that are not really of any need such as Hax or any of those expensive 5*'s that will give you a lot of clintz while not wrecking your chances of making a good ELO deck.
Possibly make a Montana-La Junta deck if you like.
There's a good one here
called Montana | La junta
With the money from the sales(mentioned above), you could easily make a similar one seeing that you already have most of the cards needed.