Is there a faster way to get better items?

Now what I have been doing, I wanted to keep on working on the first boss in the campaign. Right now, money is not the biggest problem for me. But, I really haven’t been getting a lot of items that could be useful, so what I am hoping for is for some advice.

you can buy boxes and upgrade your current items

Well I did say gold was not my problem as of right now, so what I was hoping for is maybe if I could get a better strategy rather than just "Buying them:

try farming an area in the campain

I said I was farming on the first boss level. Since all fortune box drop rates are the same.

well if you have tokens you can buy the preimuam boxes

or fight in the arena

Ramboy is the best way, seems like you are already doing that. Besides that, daily missions, ads for tokens, and raids. Only buy premium packs, and only buy during sales. With this strategy you can usually get 2-3 new legendaries per month.
Oh and farm the shit out of item portals