Skip the algaecide. Most of them contain copper, and that's what stains liners and turns hair green.
Nearly all water issues are the result of insufficient chlorine. You can safely add 3 ppm of chlorine per day by using plain old laundry bleach. Just be sure it's not the scented or splashless kind. Just regular bleach. Use the Pool Math app to determine how much bleach to add to raise your FC by 3 ppm for the volume of your pool. Read the label to determine the concentration of chlorine in the bleach. If it doesn't say, it's probably 6.5%. If you buy the liquid chlorine for pools, it is often 10%. Just figure how much you need of each and see which is cheapest.
Once you get your test kit, post the readings and we can give better advice from there. But this should carry you for now without things getting much worse.