Hanna and Milwaukee have some good lower priced meters to start out with but you will also need some calibration solution and a bottle of PH Up & Down to adjust the PH as needed. Some meters need calibrated weekly, bi-weekly and some once a month. Lower priced meters tend to not have automatic temp adjustment for water temp and also usualy arent waterproof like the higher priced models. Some do just a single point calibration and thats usualy works for most people. A 2 point calibration is more accurate if your water has a low PH to start with or nute mix drops the PH to a lower reading around 5 or less but most probably dont run into that. Bluelab also makes some really good meters but are more pricey. My Bluelab Combo Meter costs a little over $200 and I have no regrets buying it, gives fast and accurate readings in about 30 seconds and only needs calibrated once a month. My firt PH meter was a Milwaukee Link Below) and it was a good meter but my nephew needed one really bad so I gave it to him and upgraded to the Bluelab. I ordered from the site below. http://www.testequipmentdepot.com/milwaukee/ph-meters/ph56.htm
The pH level is much more important in organic soil gardens than in chemical hydroponic gardens. The pH dictates the environment of bacteria necessary to the uptake of organic nutrients. If using litmus paper, collect soil samples that demonstrate an average of the soil. Place the samples in a clean jar and moisten the soil samples with distilled water. Place two pieces of the litmus paper in the muddy water. After 10 seconds, remove one of the strips of litmus paper. Wait a minute before removing the other one. Both pieces of litmus paper should register the same color. The litmus paper container should have a pH color chart on the side. To learn the pH, match the color of the litmus paper with the colors on the chart to get a pH reading. Litmus paper will accurately measure the acidity of the substance to within a point. The pH readings will not be accurate if altered by water with a high or low pH, and litmus paper could give a false reading is if the fertilizer contains a color tracing agent. Electronic pH testers are economical and convenient. Less expensive pH meters are accurate enough for casual use. More expensive models are quite accurate. Pay special attention to the soil moisture when taking a pH test with an electronic meter. The meters measure the electrical current between two probes and are designed to work in moist soil. If the soil is dry, the probes do not give an accurate reading. I prefer electronic pH meters over the reagent test kits and litmus paper because they are convenient economical and accurate. Once purchased, you can measure pH thousands of times with an electronic meter, while the chemical test kits are good for about a dozen tests. Some meters measure the pH perpetually. Personally, I like the papers because you don't have to worry about them breaking like an electronic one. Plus they're cheap.