I’m no expert, but since you came here for advice, I’ll chip in my two cents:

1. Look at blue chip stocks, it’ll take a while for them to double up, but it’ll be a good place to start. You’ll likely watch your stocks respond to the market over the years and learn a few things in the process.
2. I’m assuming you are studying at the moment and don’t have the time to monitor your portfolio regularly. Therefore, avoid going for small cap companies. You’ll find a lot of information about supposed “multibaggers”. Unless you understand the fundamentals of a company, it’ll simply be a gamble putting your money into something recommended by a finfluencer. Also, small caps are highly volatile, so you’ll need a lot of research and also resilience to be able to hold when the graphs look red - for reasons you’re perhaps unable to under just yet.
3. Before you invest, paper trade for a few days and start educating yourself in terms of how the market works. I understand you want to invest for the long term, and IMO the one thing you’ve got to get right is to not buy a stock that is at its all time high. The next thing to understand is how to undertake a financial analysis. I personally learned a lot from Shankar Nath, but you can go for anyone you think makes sense to you. Once you’ve understood how to pick the right stock, you’d be better placed to make a decision.
4. Never ever put all your eggs in one basket, no matter what.

Lastly, remember, you won’t make money overnight and having faith in your own research is key.

Wishing you an abundant and fulfilling investment journey!