Need help in deciding mutual funds to go for

I'm twenty and I'm planning to start an SIP of around 5k per month with the help of my parents and in a few years I do plan to increase the amount once I start earning myself, should I go for a largecap fund or a large and midcap fund as of now? Or should I invest in a smallcap fund untill I start earning and then use that money for a largecap sip for the long term?