From top to bottom:

HoTT

Casting timer (useful to watch if your slow-casting spell will land before the target dies)

Target health bar with percent

Consider color just below it

Target name written large

Buff icons (same size as my tinybuff window and tinysong window icons)

First 12 buffs are centered under the target, the next 12 in the lower right corner. That's enough for PCs and group targets, but on raids the rest of the buffs fill in the right side, and then the left side.

Since it's transparent I've included a faint outline around the edge, so you know where not to click. You can change the color of it (right click, then choose background tint color). I usually leave mine black but it also looks good in red, white, or purple.