New to pool maint. Need help with chlorine level

[Jonahj]

Due to cancellation of a beach trip this year I went and bought a 18ft above ground pool at Walmart. 6450 gallons. I also bought that Clorox 6 way test strip. Yesterday the Clorox app told me to add pool shock, chlorine stabilizer, and hardness treatment. I added the shock and stabilizer yesterday. Nothing for the hardness because the directions said to get the chlorine and ph level within range. So today I tested it 4 times. Only once did it read my stabilizer at 50ppm. The other three it was 0. My last test read this:
Total hard-500
Tc-5
Free chlor-3
ph-6.8
Total alk-180
Stabilizer-0

Now it tells me to add ph up, hardness treatment, another 2.69 lbs of stabilizer, and more shock.
This is where I’m like “what the heck” I added the shock yesterday because it told me too as I had 0 chlorine. If it did that to my level why does it want me to add more at the same amount today?
What do I need to do? 6450 gallons of water isn’t cheap lol

[Denniswiseman]

You really need to get yourself a decent FAS/DPD test kit (Taylor K2006c or TF Testkits TF100 in the states) to get accurate results as maintaining an appropiate shock level means testing quite often during the day
Chuck those guess strips away
In the mean time get your water tested at a pool store and let's have those numbers
FC:
TC:
pH:
TA:
CH:
CYA:
Use these common products to balance your pool
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA