Large medium small cap funds

I recently started investing in niftybees which is nifty 50 index by nippo. I plan to diversity and take higher risk, so I m interested to invest in large cap, mid cap, small cap as well. My capital is around 8 lac. Time horizon is long term 15-20 year. For nifty50 I have came across niftybees name s several times, so it was easier for me to decide. But for large/medium/small cap there are so many option from different institution, so I m confused. Do you guys have recommendation? Also on side note, what's flexicap fund? Should i also think about nifty next 50? Or simply invest all fund only in niftybees as my time horizon is long.