For most people who have been playing the game a while, Arena, and GW are the only actual gameplay, and in both cases because the best rewards in the game come from these two events no one wants to take any chances.
I wont go into GW here cause thats a separate issue, but for Arena I would like to see it restructured to something more like Clash of Clans, that is to say you can attack as much as you want, but have the rewards significantly reduced. BUT add in small rewards for every win, have it work like a normal ladder where the more wins you have the higher you climb, and the rewards get slightly better, but set no limit on how many fights you can do.
This gives you something to do anytime you log in, but by significantly reducing the rewards you are not creating a huge game imbalance by letting people do it whenever they want.
Just as a suggestion I would maybe say change it to:
Daily achievement, complete 10 matches in arena: Reward 45 crystals 400 arena tokens
Daily Achievement Win 5 arena matches: Reward 100 crystals 400 arena tokens
Each win rewards 10 arena tokens and 1 crystal
If you just go in and do 10 matches you get enough crystals that you can do your 2 energy refreshes and 1 cantina refresh per day (assuming you do GW and all other daily activities) if you want to do more you can grind slowly for crystals and arena tokens ie giving you a reason to play.
As for a reward for the leaderboard, end of every week hand out some rewards for what tier you ranked in over the month, make it credits or training droids or something like that, ie worth fighting for, but not the be all and end all.
Thats just my humble opinion.