Sorry I haven't replied in a few days, but I was looking at gobies and pistol shrimp. Would it be possible to do one of each and a clown or firefish? At my lfs I found a used 29 gallon tank, stand and light for $125, but mom said I could do better.
A sump is not required on a 29 but if you have the time and cash it's always a bonus! And yes you could just do plenty of live rock for filtration. As for the cycle pick up a salt water test kit (liquid if you can) and text throughout. After a spike in ammonia, followed by nitrites you will end up with high nitrates, hopefully much higher than 10ppm
There is not an exact number the nitrates will reach. As long as amm and nitrites have come down to 0 you will have high nitrates (depending on how good a cycle it was) some get 20ppm some as much as 80 or 100ppm then you do a big water change before adding your first fish