6 star lumi, and drop some devilmon into her. She'll carry you very far in both Famion, Giants B10, and Dragons B10 assuming you have some decent runes... mind you, these aren't game breaking runes. Look up how other Lumi's are runed in threads.
Once you have your Famion Hard/Hell farmer in Lumi, bring up your support teams to 6* (Ahman, Bella, Shannon, maybe Bernard) so that you can farm Giants B10. After that, I would focus on folks that will help with ToA and HoHs (Baretta, Jojo, Hwa).
Arena: If you're in 1400-1500 zone, just stay there for now. You need to get some six stars before you can really hold solid conqueror ground IMHO. It's not worth it yet with what you have.
Crystals: Once your Lumi can carry you through Dragons B10, it's been demonstrated that the refill/shop refresh path is a better method of pulling mystical scrolls. Double XP is great if you can farm famion hard with one farmer, or famion hell with 2 farmers. I'd save up a bunch of two star/three star summons, and then turn on double xp and refills to build your six stars fast. You could benefit from a few more lucky premium packs, but it's definitely risky in terms of whether you get anything good.
Glory: You've got too much glory points. With that much, I'd focus on spending it on Speed and HP boosts, both which will help you in Giants/Dragons.
Mana problems: You should have very few... where are you spending your mana? Farming Famion Hard/Hell will generate tons of mana, and farming Giants/Dragons will generate even more. Follow these rules - Only buy good six star runes in shop, only buy mystical scrolls, only attempt up to six rune upgrades per day... you should build your mana stores to about 2 mil, and then once you have that, burn off any excess on rune upgrades. The 2 mil helps guarantee you'll be able to get any great runes that appear in shop in case of back to back great runes....
HoH: It's definitely a good idea. Light sylph has pretty decent stun/CC, useful in future HoH and ToA. Get one, figure out if you have enough time/energy/crystals to get 2, but don't waste time if you aren't able to get the 2nd... it would be terrible if you were short a few pieces as the energy wasted is huge.