Not withstanding some deals around the net, that price range ($25 US) will not get you a "good" or "reliable" ph tester that will work for both soil and liquid solution testing. I personally will use a pool kit before trusting cheap pens to measure conductivity correctly ...
Plenty of recommendations and arguments on the best ph pens for various applications. Simple water testing versus solutions testing is one of the break over points. Some of the cheap(er) ph pens work well enough if you can keep them calibrated for straight up water. But fail miserably on nutrient laden solutions and "other" liquids.
Look at Hanna and keep in mind they offer commercial and "professional" offerings for a starting point. Figure around $100 US or less depending for just a ph pen to test water and most basic solutions.
Depending on your needs (growing method) this is one area where you bite the bullet and spend for the best tools you can possible afford. Not most expensive, just best. This includes having soil tested by a lab occasionally (if you're in soil), etc if you're wanting to really know what's going on. Basically because a good microscope, desktop mass chromo, sterile boxes, misc lab equipment, etc is way out most people's league. That and learning how to culture and identify most of what they can provide of course takes some serious investments over time and in equipment.
As a side note testing for things like DO (dissolved oxygen), chloroforms, chlorine compounds, water hardness including other dissolved minerals, and other things can be as or more important for finding out why some things are not coming out as expected. Especially when making teas and the like. Again, lots more tools and expense to dial in your approach. Or start with having your water and soil sources checked by an ag lab twice a year or with significant changes for far less than acquiring tons of equipment or vague test strips.
Cheers.
