My advice might not be the best, as i am pretty new also...so if there is any other conflicting feedback, then listen to experience!
i would say rent ANY gold foil as cheap as you can. i'm not sure, but i believe a single gold foil would give you the power to go up to the next level...(i didnt math that). i do know you can rent them pretty dang cheap tho. and i think they offer the highest power/cost ratio.
I'm currently in the middle of my second full season and hope to make it to gold soon...it's like bashing my head on a glass ceiling LOL.
good luck!