My questions are below if you can help please
1. Do i do the same and open various wallets and buy the coins that way or do I have to use an exchange like Coinbase or Binance to buy the coins?
2. If/when I want to sell the coins do i withdraw via the wallets or do i go onto an exchange and sell? Then transfer the money to my bank account.
3. Is there a secure wallet I can get with can hold all the coins in 1 place or do i have to open multiple wallets?
Depending on the country that you reside OP you should open up an account on a cryptocurrency exchange. Binance is a cryptocurrency exchange that is available in most countries and it is highly trusted. Open an account on it and then you can make purchases of Bitcoin and other cryptocurrencies using your local currency. If cannot access Binance or do not want to pass KYC then you can open an account on MEXC Global. Then do not ask you to pass KYC for making a transaction of up to 2
BTCThe second thing you need to do is download Electrum wallet for storing Bitcoin. It has a mobile and desktop version, choose which one suits your requirements. For Ethereum, meta mask is a good wallet and for storing multiple cryptocurrencies, you can go for trust wallet. Do remember to create a backup of your wallet and keep the seed phrases somewhere safe as they are the key to accessing your wallet in case if of accidents.
When you want to sell any cryptocurrencies then open your wallet and send it to exchange wallets. You can find tons of videos on YouTube on how to receive and send cryptocurrency using any of the wallets mentioned in my reply to your post.