It doesn't really matter what you get, but you get an extra hit with a war aviary but it takes an additional 5 mins to regen.
If your next land is less than a t3lv2, don't get t3s yet wait till your lands are more than lv2 tier3s (or lv3 tier 3s) before you buy any
What relentless said. You're way too small to buy T3's right now. Keep expanding and putting up T2's for now.
My advice: Keep building forges/beastiaries as well as some guilds until you unlock T4 buildings at land 25. T3 honestly is just a waste of gold as T4 is sold at a discounted price since T5 came out. At land 25, replace your T2s with T4s, I would suggest you building the balanced ones (CoE). One of the most important things: Upgrade those guilds to lvl4! And keep checking if you have enough gold in allies to be at max ally bonus plunder, you seem limit to me.