The current situation of alts is weak and volume also down accumulate our suggested coins in dip i will suggest you today 4-5 dip entries. Buy partially that coins to get lower average entry. 
Dollar cost averaging is always a good idea. I must admit I hadn't noticed lower volumes though, all I saw was that whole market volume is really high, but yes, that does seem to be mostly BTC... which makes sense as often BTC is the first coin to rise in any market recovery.