never hurry to make purchases and sales of existing bitcoin have. make sure that when you sell your bitcoin can earn a profit margin on buying price the previous bitcoin. it will determine whether you will lose or gain.
taking advantages of the margin price is indeed good but i guess OP is actually reffering to altcoin trading even though bitcoin trading is also profitable
best alt coin for me to invest is ico's you can also choose what icos you are going to invest your money visit the marketplace (altcoin) and find what your gut's thinks that you can make some good money.
but beware with shit ICO which only scamming people around after gathering the bitcoin. they were exist and just be sure to invest on the right place