help finding an inexpensive multimeter to test earthing/voltage

hi new to grounding/earthing and want to actually see my voltage numbers without breaking the bank. I bought a cheap multimeter innova 3320 on amazon but it was obviously not reading correctly (not getting higher near laptop, not going down when touching grounding mat)

so if anyone can suggest a known working for this purposes multimeter that is not that expensive (this is the only thing I anticipate using it for) I would greatly appreciate it.

Thanks Tweet