I would add as much LR
as financially possible when you are first cycling the tank. People normally aim for 1-2 lbs per gallon. If you add it now while the tank is cycling, then you don't have to worry about cycling it in another container, or starting another cycle inside your established tank.
As far as sand, live or not, it is mostly on personal preference for how deep you want it. It may also depend on what you are planning on keeping in the tank also.
I'm not sure you already have this, but you definately need a testing kit. Go ahead & through in a cocktail shrimp from the grocery store to help with your cycle. You'll need to let you tank cycle completely before you can even think about adding anything living. Test everyday to every other day & you should be able to see the spike in ammonia, nitrites, and then finally nitrates will show on the test kit. Once everything is back at zero, you can begin adding livestock. BUT SLOWLY!
How long is this all going to take? Probably about 4-6 weeks. Some people experience a shorter cycle, but don't get your hopes up. The cycle is the first test of patience, don't rush it, or you will regret it later
Some of the mods, I'm sure, will be behind to post some beneficial articles for you, but hope this gives you a head start. Good luck!