Moreover if you want to remain more secure while doing BTC transactions, then use mixer for safety.
I have assured him that there is no need to worry too much about the bitcoins he buys on P2P exchanges because the mixer can help him obscure the transaction history. If the OP is in doubt about where the bitcoins are coming from, then he can ignore the seller and not deal with him.
Also if you don't feel purchasing Bitcoins from P2P deals, then give a shot at popular exchanges.
Since the OP seems like someone who likes privacy then I don't think suggesting he buy bitcoin on a centralized exchange is a good idea.