What fund do I start to choose to invest in SIP for three years with a high-risk appetite?

First, please validate your risk appetite by taking an assessment here. Often we think we have a high attitude to take risk, but he ability to take risk may not be there. The converse is also possible, high risk ability but very low attitude and fear towards risk.

Assuming you do have a high risk appetite, i would recommend am SIP in a combination of multicap mutual funds and midcap or small cap funds. This combination will vary based on your risk profile.

If you can take higher risk, then one thing you can do is to start investing more when the market starts corrects, i.e. in bear markets. This will test your resolve as well as potentially generate outsized returns!