I think brawl is the best if you're looking to be effective with wild cards. It's a less competitive format that you'll be familiar with if you have played edh, and you will spend less wildcards solely because you can only have 1 of each.
As for what I play, when I started I crafted the best mono red standard deck I could and farmed my 15 wins of the day until I could afford to build any brawl/standard deck i wanted with my wildcards. But that path requires you to really like playing red.
Historic is expensive and the only format I do not recommend.