Which weapons should i use? going from common to ultraRare?

What is your playstyle, and prefered character?

Just buy the 5K boxes untill you max out that part of your manifect, should give you some uncommon weapons as well. Ultra Rare weapons does not mean they are much better, if at all.

The Hurricane (SMG) is nice, as is the Black Widow (But it does less damage than the regular Widow) however you can do fine without them. The only real upgrade I can think off, is the Pirana (Auto-shotgun)

The best weapon so far for close quarters is the Charger X. The Equalizer (Rare) is also good. Everything else that has rapid fire below UR sucks as far as I can tell. Completely avoid AR and the only Shotguns that is viable above Bronze is the piranha.

Melee <> Power.

Well actually, Melee >>> Powers but what I'm trying to say is that punching stuff in the face isn't the same as playing a Powers character.

I actually don't think you can play a Powers character in MEA and do well. Not unless/until they massively boost the damage that power combos do.