Gotta go with suppressor! If not now, then when? You can get acc. for AR one at a time to break up cost, look long and hard for that super deal on a handgun-but that tax is never gonna budge! Unless it goes up!
In my humble opinion, new gun day is one of the best days of the year, so I chose new handgun. Plus, I'm also more of a handgun guy than an AR guy, so it would be an easy choice for me.
Pick up a 22 LR version of something you already have such as am S&W M&P 15-22 or a GSG 1911 in 22. It will be a new gun and allow you to train with the same controls and all at a cheaper price on ammo
I will vote other. Get a 7.62 can so you can decently suppress an AR and if you feel like suppressing a .308 or something later you are good to go! Cans are pricey, id go for biggest bang for your buck now, then maybe a while later get a smaller can(if you feel you NEED it)