The Helmet is a bit "squished" out of proportion and the undersuit has been described as very much like padded pajamas. The armor itself is not bad, the plastic is just very thin.
If you decide to go with it, plan on getting a new helmet, undersuit, and reinforcing the armor.
As for kits, unlike other Fandoms there are not a lot of "Kit" makers out there for Halo costumes, in the sense that Kit means a sort of Mass Produced ready to assemble set of armor.
Sean Bradley sells an excellent ODST kit, and we have several vendors of Resin Cast helmets, but beyond that Halo costumes tend to be Do It Yourself or 1 off commissions. There's a lot reasons for this, the sheer variety of Halo armor, the fact that it was predominantly digital assets and as such not as easy to reproduce as a costume that was mass produced for film or television.
Regardless, outside of the commercial products like the Disguise Halo 4 or the Rubies Halo 3, or Sean's ODST Kit, it is best to plan on commissioning an armor set, if you do not want to go down the DIY route, which is perfectly fine.