I'm still relatively new, but here is my advice:
Pre #1) Use all fleet materials credits wisely - these are in incredibly short supply as you progress early.
1) Save at least 800 fleet arena tokens before your reset in case Vader and/or his ship are available in fleet arena store. Buy these at all costs.
2) Ghost & Phantom - since you have Phoenix already, getting these ships to 3-4 stars should bring your arena ranking to top 25 by themselves. These are periodically in the fleet arena store. Once I got mine to 4*, I pretty much abandoned them for now but kept my Phoenix leveled.
3) KRU + Silencer - both are on the same cantina farm, so it will go very quickly. Get both of them to 7* asap.
From there, it really depends on what you want to accomplish. I went all dark side ships so I could farm zetas as soon as possible (need 5 x 5* dark side ships + executrix). I have about a 50/50 win percentage against like light side ships depending on RNG, but normally finish #2 by reset everyday. One guy is over 60k stronger than anyone.
Like I said, I'm new, but here's my profile in case you care: https://swgoh.gg/p/539284339/