See here

https://www.dell.com/community/Laptops-General-Read-Only/inspiron-n5050-cpu-upgrade-help/td-p/3978721

Welcome to the Dell Community @Indunil1996 

The best CPU for your laptop is the i7-2640M. (Same TDP)

https://www.cpu-upgrade.com/CPUs/Intel/Mobile_Celeron_Dual-Core/B815.html

There are faster CPU's but the TDP is higher and the system would run a little warmer.

2 x 8GB 16GB max for the memory.

I like using DDR3L but DDR3 is factory.

Best regards,

U2