In general you want to follow the rule that you do not want to store your coins in any 3rd party wallets (including exchanges) if possible. Keep the coins you intend to trade actively there only, and make a cold storage wallet for each of the coins you intend to store long term. Make multiple copies of these cold storage wallets, and store some away from your home in case of some unforeseen circumstances such as a fire or natural disaster.
If you want to make good buys, research the coins before investing in them. Look for a solid development team, an active community, solid economic policy, and a protocol that offers unique utility. As far as making good investment picks as a newbie, look for coins that have a large number issued, inexpensive per unit, have not risen yet significantly, and have a decent trade volume. One good pick in this arena could multiply your investment in no time. Good luck!