Long-Term (10-20year) Investing

Hi, I recently completed my post-grad degree and is now working full-time. I am hoping to create a long-term portfolio but I’m not really sure where to start.

My plan is to start placing funds in a monthly basis in select investment items but I’m not sure what are recommend. I’m looking for a high yield and I’m okay with fluctuations since this is for a secured funding.

I have a separate account for my crypto portfolio (purely spot). I am currently thinking about mutual funds since past experience gave me around 15%+ yield for the past two years.

Just wanted to ask if the group has other recommendations since I’m trying to diversify my portfolio as much as possible. Im planning on placing recurring amounts on a monthly basis rather than a bulk fund. Thanks!