you can get a multipurpose PH tester, watering tester & even light meter for under 20 bucks. i think i paid less than $15 for mine locally. if you want the most bang for your buck in lighting, use the difference to get 3 to 4 shop lights & cheap bulbs and just SCROG your plant(s) flat. really, if it's just 1, you could get away with just 1 shop light with a small "net" under it about 2-3 inches from your plant tied down SCROG style. bulbs might be more expensive now, but you used to be able to get a 2 pack for something like $4 and a shop light for $12-$15 at department stores. if you can find them though, philips "hi vision" warm daylight (i think they're called) bulbs are really bright and have an orangish cast almost like a sodium bulb.
some day, i should do a shoplight scrog as i have several shoplights just to show what can be done on the cheap. the very first grow i did actually was 40 bagseeds from 1/2 as many strains that i just "topped" repeatedly for daily leaflet trim under a pair of shoplights. i liked that trim better than ANY of the stoner bud on the market. putting shop lights on a timer & training your plants horizontally should work. despite what everyone CLAIMS, i got great bud out of my 400w halide with no sodium and an orangish 4" tube should have a broader spectrum.