Get a good test kit and test test test, until you get the hang of it. Trust me, it really won't take long if you use the resources here. Pool Math, FC/CYA chart, etc.
Get rid of the tablets and just use bleach. Regular bleach 8.25% (Sodium Hypochlorite) with no additives is what I use. Most pool store chlorine has Stabilizer/Conditioner which raises your CYA. FC levels are dependent on what your CYA is. The higher the CYA, the more FC you need but the longer the FC will last. It's a balancing act and you'll need good numbers from a good test kit to get those. Most here recommend the TF-100. I have the TK2006 these will allow you to see FC levels far higher than the cheap color matching kits as they rarely measure over 5 and you'll need to read higher than that at times to get it right.
Test from the beginning, post your numbers here and these guys will get you going in the right direction straight away.
This is my first year and I'm already understanding what I'm doing because they tell you WHY! The pool store will never do that for you.