JBJ 28g Nano Skimmer

[Money pit]

With a small tank, unless you want SPS, why not just go with big water changes once a week.
I kept a 30g skimmer less tank for about 5yrs. I would change about 50 % a week. I don't think you would have to change that much unless you have a lot of LPS that you feed often. There are some great skimmer less tanks out there. Just be sure the temp, PH etc. match your tank.