Can I start trading with $100

It strongly depends on how much leverage your broker allows you to use. Brokers with low leverage like AvaTrade, TD365, Trade Nation, Pepperstone etc. will require you set down a high cash collateral (aka initial margin) before you are allowed to open a trade.

However, brokers with high leverage like FxPro, Exness, Just Markets, etc. will require a lesser amount in collateral before you are allowed to open a trade.

So, the answer to your question is yes you can start trading with $100 but better use a high leverage broker.

I began my trading journey with $100, trading around 0.05 lot size. So, yes you can start with $100 but keep the lot size small so you don't lose all the $100 in one day. Have a daily loss limit (like $3 a day) once you reach that limit, stop trading and wait till the next day.

Yes, a beginner can start trading with $100, but the main goal should be learning, not making big profits. A small amount is actually good for beginners because it teaches discipline and reduces risk. You must use very small position sizes and understand that losses can happen quickly. I am not really in support of leverage for a beginner.

But high leverage is also dangerous for beginners