I don't understand, so I buy the coins on Kraken but I sell them on Binance ?
If you're planning on selling the coins back at some time then use Kraken also if you're going to use Kraken to buy the coins anyway. No need to unnecessarily use two different platforms. Just remember to use a non-custodial wallet for safe keeping while you're waiting for an opportunity to sell.
From what I see, Binance seem to have a lot more coin available...can I just buy and sell on Binance ? are the fees higher than Krakens ?
Seems binance have cheaper fee and you also can reduce fee further by using BNB,but you can't simply pick random exchange and buy random coins.First you need to decide what coin you are going to buy,if you just planning for day trading then binance would be better but you have to learn about the basic indicators like RSI and bollinger bands for getting idea of when to buy and sell.
I am looking to buy around 10-15 type of coins and keeping them for long term 2 years +