If you compound your soil with a bit of dolomite lime, you don't need a pH tester at all. You can get away without measuring TDS if you learn to "read" your plants and feed them when they show appetite.
The route I'd recommend for a first grow is to go with a complete, no-additives-necessary soil like the Supersoil discussed in the Organics subforum. You'll spend less on the ingredients for that than on the testers. My 2¢ ... cn
<edit> I think the flushes are a gimmick, myself.