Where to start with forex trading?

Try tradingwithrayner.com, he's also got a youtube which breaks down FX trading for you into understandable language and concepts. A lot of good beginner/entry-level content which is all free.

Recommended amount of money - you can trade FX with a small account size but you need to find brokers that can trade nanolots/microlots. You'll also learn to use leverage, which is basically borrowing money to get a bigger exposure (and profit/loss) on your trade.

But before you trade cash, practise trading with a demo account for at least 6 months to a year.

babypips.com is a good resource which covers forex trading. Broker for Forex, I think OANDA is pretty reputable.

Recommneded amount of money to start really depends on your own fianancial situation but I would advise you start paper trading first. If you can be profitable over maybe 6 months, then you can consider moving to a real account.

Disclaimer: Forex trading is heavily leveraged usually because forex movements are generally very small within the day. As such, leverage is necessary to make it worthwhile. However, this greatly increases your risk of losses as well. Do take note of how your P/L fluctuates in your paper account and fully understand the amount of leverage you're taking on before entering a real account.

For a more personal take: I was once fascinated with the gains to be made in forex as well. I tried for a few months on an OANDA paper trading account but eventually just went back to stocks which I understood better. In forex trading, you're mainly fighting against algos so honestly it's tough to win unless you have your own algo or you trade over longer timeframes. Just my 2c.