Mining of altcoin is quite good idea for getting good ROI with mining cryptocurrency.
But mining is depend on many factors as below :
1 ) Which scrypt you use
2 ) What currency you mine
3 ) What is difficulty level
4 ) Block size
5 ) Block height
6 ) Block Reward
7 ) Time to solve one block
8 ) Increase % in next difficulty level
All things makes impact on mining.
Also you have to know which currency to mine as per current market cap, price, exchange rate and volatility.
As already there are some sources where anyone can find which currency mining is profitable at
https://www.whattomine.com/ here on site we can get information of all currencies with their actual price and also make calculations of ROI.