First off, welcome to Aquarium Advice!
You may be alright using tap water but RO
is really recommended (I know this firsthand
). If you really want to you can try starting off with tap, but just be prepared to do a lot of PWC
water down the road if tap isnt working out.
Generally you should aim for at least 1 lb/gal
but that's just a guideline. You can get one piece of live rock and the rest base rock - as you guessed correctly, the live rock will seed the rest of the tank with bacteria.
As for cycling, the Articles section has a great writeup
. The recommended method is to use a piece of raw shrimp or fish food to generate ammonia, which will then go through the cycle and bacteria will be established. This could take anywhere from a few weeks to over a month.
With clowns you are not limited that much with tankmates. Basically, you could choose almost any nano fish that captivates you. I'll add another post when I have a bit more time with a few suggestions, but off the top of my head, you could get firefish or chromis.
Hope this helps, atte.