Sorry if this is a really stupid question


I'm going to have a go at the no drill fuel guage earth (guage only showing half full when we have a full tank). I'm completely non techie/DIY but trying to learn (in fact last week I managed to replace a mixer tap in my kitchen by following a you tube vid


Anyway, drilling holes is way too scary for me so I had a look underneath the van, located the fuel tank and found the pre drilled hole in the lip and the other on the chassis.
Going to go off tomorrow and buy the wire, connector and nuts and bolts.
My stupid question is, what type of wire should I buy (does it come in different guages?) and what guage of ring connector? Also where would I buy this? Maplins?
Thanks as ever for your help.
Sara