If you could leave any knowledge at all on trading...
From what knowledge in altcoin trading you have been now so far?
If you could leave any knowledge recommended sites...
Recommended altcoin exchange platforms depends on the altcoin you have chosen to play since not all exchange supports all altcoins. Like in Yobit, almost most of the coins are there including shitone. Poloniex only listing altcoins with active volumes etc.
If you could leave any knowledge good altcoins...
This is the challenge. No one can give you an accurate answer about good altcoins to invest. Most of the short term traders is looking at the newly COINS on ICO and they are taking the risk.
Since most the new coins can be acquired by cheap prices, they can bag more of it and will now play on an altcoin market trading.