New to salt - substrate questions

I'm planning and buying supplies for my first saltwater tank, a 29 gallon. I'm going to use a sand substrate, but I've got a couple questions before I choose what kind to to buy. What factors do I need to consider when choosing grain size? How much will grain size matter? What's the best depth without getting into anything like a DSB? I would like to keep some kind of goby, so that may be a factor in choosing the depth. I'm totally new at all this, so forgive me if my questions are kind of obvious. Any input is appreciated.

 

I've not looked too deeply into what fish I will choose yet, but I was thinking more along the lines of a shrimp goby. Do these also require a DBS?

 

How much live rock are you planning on using? If you have more live rock you can go with a more shallow sand bed. if you have less rock you would want a little more sand. I have 80 lbs in my 120. I'd recomend Ocean Direct sand. It was a good clean sand to use. They claim no rinsing is needed.

 

I like the look of a lot of rock. As far as pounds go, I'm not really sure, as I haven't ever kept a salt tank. I would estimate over 50 pounds, but I could be way off. I want it to have a decent amount of rockwork though.

 

I don't know if you are planning on a reef tank or simply a FOWLR (Fish Only With Live Rock). However, if you are going to go reef, remember that many corals you purchase will come on LR (Live Rock) so don't overdo the LR purchases.