I dipped a pH paper in lemon juice as a test, the color did not change much or obviously and I was in doubt when looked at the chart and found It's hard to determine which one is shares the most similarity in color to the paper...

I was thinking about getting a digital pH meter, something cheap and small (pocket/handheld). are these way too expensive? to what aspects pay attention when buying? generally guide me please. or I don't know maybe my pH paper is too old or poor quality and I'm better buying a new and better pH paper? The one I tested is way too old (maybe 7 years), I found it in basement with lots of dust on its packaging.

I bought a chinese water pool ph meter on ebay for 10€ a few months ago and it works like a charm, it's limited to a ph range of 2-13 but
that's definitely wide enough for our use.

Hi there Eranik
My advice would be to invest in a digital pH-meter! Maybe you can check out different online hydroponic stores. Hanna Instruments makes pretty reliable meters in my experiance and if it's only for measuring pH it won't cost you that much! If you choose to buy digitally you have to be aware if it's a two- or one-point calibration apparatus and buy calibration liquid accordingly.
I hope you can use this!

Good luck!