My 2p.
Don't upgrade parts on your Ion. Save your money and then upgrade your ion in the future to a Proto / Dye / Etek / Ego. Some very good markers for some very silly prices.
Enjoy what you have got, spend your money on playing. And as for mask, I can recomend a pair of E-Vents.
Yeah im not gonna stick with my Ion forever! altho i might keep it, ill head for a more high end marker once im playing more, only just starting off so the ion is all i need untill i hit it up more extreme.
Ill also have a look into some E-Vents as a few other people have suggested them.