I think we all dreamt of being TKs at first. From the first viewing of SW (The original) to the first time we discovered the 501st.
But, something about the TD is awesome and as mentioned before, it shows that you are a TRUE fan by the attention to detail on the different versions of the film seen armor.
Don't get me wrong, TKs are AWESOME and I do hope to become a CENTURION one day (EIB first of course) not to mention that I started out in the 501st as an ANH STUNT TK, But a SANDTROOPER just looks downright dirty and mean.(C'mon ...BFGs?!)
They also look like they are capable of keeping law and order on a HUTT controlled planet, laying waste to Jawas, Tuskens and uncooperative moisture farmers. (not that I support actions like that.)
Anyway, I would personally start off an armor arsenal off with a TK just to have that iconic 501st standard issue trooper suit out of the way. Then I'd start adding various suits after that. Just my opinion. Any decision will be cool, no doubt. Good Luck!