this is for a 29 gallon tank?
a hang on skimmer would work, ive never used them though. if memory serves me i remember reading/hearing the aqua c remora being decent. reading online reviews/googling will help with a skimmer. all my skimmers have been over $100 except a MTC skimmer i got used from a buddy that he gave me it for $100.. the thing was like a $350+ skimmer lol.
if your going to do a tank running a skimmer i strongly suggest investing in a decent piece of equipment. alot of research is key, as ive stated read online reviews.
skimmers, lights, and flow are the 3 most important pieces of equipment.
check your area for a local reefing club. you may find some great deals there.
if this was my 29 gallon tank ( ofcourse we know it isnt, but lets pretend
i would drill the back glass granted it isnt tempered which it shouldnt be, install a glass-holes.com overflow box. i would DIY a 20 gallon long tank into a sump. i would run a small in-sump skimmer, possibly a ASM mini G or something similiar. i think i would do 6 bulbs t5 lighting but with a DIY retrofit kit from hellolights.com
i would pick up 40lbs of dry rock/40lbs sand from marcorocks.com, fill my tank with most, if not all of the rock in a unique structure and not just a straight wall. i would add sand until i acheived a 4'' layer of sand. i would use 2 hydor k powerheads, or even better 2 ecotech mp10s if you could afford them.
for livestock i would have 2 clowns, a goby and pistol shrimp pair, skunk cleaner shrimp, a mixture of different kinds of snails... i would add one more fish but cant decide, maybe a captive bred bangaii cardinal. the rest of my livestock would be a mixture of corals.