Don't just go with the cheapest.
Go with 100% clay untreated cat litter. MOST brands of cat litter are treated with deodorants, disinfectants, clumping agents, etc. IF you buy those, your fish will be dead shortly after introducing it into the tank.
100% clay cat litter. I have used it myself several times, and like it just fine, no cloudy water problems.
I put 2 inches of cat litter and cover it with 1-2 inches of sand. When I fill the tank, I put a layer of wax paper on the sand, put a styrofoam plate on the wax paper, and any water coming into the tank hits that plate. Any runoff from the plate hits the wax paper.
You will have air pockets in the clay. I poked the substrate with a pencil to get as much air out as I could, then smoothed the sand. I planted my plants and they LOVE the kitty litter. Since it's a small fraction of the cost of any bagged substrate 'designed' for fish, I highly recommend it.