Arena rank on new shard

Climb as far as you can, as fast as you can with the gems you have. (Im assuming your f2p)
Higher arena placement = higher daily gem payout.

Jedi consular and Geonosian soilder (unlock cantina) are 2 toons that are immediately available as f2p and you will still use later in-game as well.

Jedi Counselor aka (jc)
Geonosian Soilder (gs)
Boba Fett (use as leader)
Lando Calrisan
Stormtrooper Han (sthan)

These characters (toons) are available to you right of the bat, and will get you started covering a plethora of things you need (arena, galactic war, events, ships, raids, etc..) not a complete team to do everything put lv that core party and as chips fall those toons will give you a head start on just about every aspect.

Gear most important,
Then character level,
And finally star level.

Those 5 above are a darn good start and require very little time to aquire.

If you would like a more in-depth description check some you-tube vids.

https://youtu.be/VDoadb8jNm8
This vid by warrior is solid gold and well put together. I highly recommend it.

Good luck and may the taint be with you!

So these 3 ranks per battle is a thing?!
OMRNG
Till 2500. Thats just rude CG.

Good info though. So one requires to snipe 2500- account otherwise it's pointless.
Hmm...

A lot of people have been reporting the 3 rank thing in bugs section. Apparently it eventually stops.

Also, I agree your advice should've been to start another account two days later.

1) If he started at almost 19,000, he should have just created another account an hour or 2 hours later.
2) This ''bug'' only lasts for the first 4 battle attempts, subsequent battles will show you much wider range of possible opponents.
3) This is WAI. Please refer to CG_Kozispoon response: https://forums.galaxy-of-heroes.starwars.ea.com/discussion/comment/713576#Comment_713576

Edit: The official term now is Arena Leaderboard instead of shard.