I am a very competitive player. In all games I play. Been playing MOBAs for 10 years now and always was top 1% of world players.
My start in this game was also bad, mediocre at best, because I did not read the guides. When I did I rerolled a few accounts and got Baze out of my 1st chromium (one of the best pulls if not the best) and then I realised...
You should play the game for fun. To be able to hit top 10 in the arena and stay there I would have to hoard free energy for 2 weeks (at least). Then hope that I dont get whaled over by paying players and have all my work done for naught.
On my 1st account I managed to keep floating around ~50 place in arena. So I get 100-150 crystals per day. Not the 300 or 500 it could be, but do I care? That is like 2 bucks a day. I am not going trough all that hustle for 2 bucks. If you intend to keep playing you will catch up eventually. So I scrapped my Baze and kept playing. Did not regret it once.
If you intend to play this game JUST for the PvP (and just arena/fleet, not even putting territory in here) then go for it.
As for fleet, the only starter character I saw mentioned by all guides was Biggs. And for good reason since he will just keep re-taunting and re-shielding himself every time you hit a target lock enemy. I am level 59 and about to go 60. I have a full phoenix squad. I am going in with the starter squad and hitting for biggs/boba/phoenix ships, in that order. I was leveling ackbar but I think overall Mace is better for starters.
I know for a fact the latest shard is pretty fresh. Maybe has 1000 people in it. A friend of mine hit 28 2 days ago and was placed 19500. So the old shard just ended. So your call.
Remember to play the game for fun above all. And this is coming from a hardcore MOBA player.