Making your own sump allows you to customize the size of each section. Petco currently has a $1 per gallon sale going on. Measure the space in your stand and get the biggest one you can fit there. With your dimensions looking about a 20g tank.
For baffles, glass is pretty cheap to buy, I would go to Lowes since they also cut the glass free for you. Silicone to stick the glass to the tank, watch that video I posted for you. Make sure its aquarium safe. GE 1 windows and doors is good.
Since your sump is quite small, its gonna be 3 sections
1st section the mechanical filtration. Filter pads works. Filter socks are better, can get a clip on sock holder and sock combo for about $25, rare to see them on the marketplace. This section. Will be small just big enough to hold the socks.
2nd is for equipment. Protein skimmer, heaters, media reactors. Skimmers is a divice that uses bubble to take poop and uneaten food out of the water before they have chance to break down to nasty stuff. Media reactors is basically a tube with two pipes, one pipe to bring water in, the water is then mixed with the media then out the other pipe. Media is normally GFO which is used to rid the tank of phosphate. And carbon to remove impurities from the water like yellowing and smells.
3rd section is your return section for the pump to retune the water to the DT.
You can have a 4th section for a refugium, some will debate forcing a small section for a refuge will have little to no effect, better to get a bigger skimmer to compensate. Again check out the marketplace for mid size skimmer rates for your tank
Hope this helps
