You will have lots of room. I have 30 lbs. of sand and about the same amount of LR in my 24. If you want a DSB (deep sand bed) I would get another 15 to 20 lbs of base sand. Put the base sand down first then put the live sand on top of it. Try not to mix it up too much. Put the base sand in and then add about 4 inches of salt water. Pour it into a bowl, that will help keep the sand bed in place. Then add the live sand. Pour that into a bowl and spread it slowly over the base. Once that it done finish adding water. Don't forget, don't add too much water. You need to add your LR and that will displace water. Once the rock is in, finish filling the tank with saltwater.
Hope this helps,
Bob