Money is the fastest way.Focus on 4 stars, I don’t know you’re profile but my best guess is that you don’t have a solid 4* team yet and already looking at a 5*.5* aren’t the magic ticket, a max 4* is about as strong as a 5* 3/45. Get yourself a good 4* team in the arena, you can just pick them up there, max level, sig them and become uncollected and the 5* shards will be pouring in from then on.