Note; Coming from a long time Hammer user that switch to Gunlance and SnS in 4U for a different experience.
Fastcharge isn't quite as useful as you might think. If the set happens to have it, then that's fine, but you're going to be getting to the second stage of the charge pretty quickly for that dashing uppercut. Compared to say receiving more raw damage, earplugs and other skills, it's very low on the priority list. And unless they've buffed KO King (another skill you might be tempted to get), you'll probably want to avoid it. The odds are the extra KO damage won't result in another KO during the fight. Or if it does it's because it's dragging on forever and you could have used Stamina Thief, or Attack buff instead.
Tetsucabra X looks to be the best early G rank hammer set. It gives you a nice Defense boost, Stamina Drain, and Sharpener. The only problem with it is you have three slots to work with, so you won't be able to gem in too much.
Najarala is another set to consider. High grade earplugs are great for a Hammer, allowing you critical time to get those head shots in while the monster roars, Tenderizer is good for smashing heads and Tranquilzr is good all around for farming monsters.
Evasion is a good ability to go for in terms of your Talisman / Gem. It's super useful for Hammer, as you'll need those extra frames to roll out of the way because you have no other way to guard. You can even roll through some shorter monster roars, negating the need for earplugs if you master it.
Marathon Runner is a useful ability to have because it will help you keep your charge as you move around for longer. You can obviously bypass this by using Dash / Mega Dash juice as well. Or making a good Hunting Horn friend.
If you have a good Destroyer talisman, it can be a great choice. All the other skills you might want, Challenger, Sharpness +1, etc, will probably be too tough to get at the beginning of G rank.
Hope this helps a bit.
