Some important things to know:
Hardness testing (whether using a proprietary kit or everyday items) is for minerals. It’s virtually useless for identifying rocks composed of multiple minerals or matrix-supported material. The exception is when you have a rock in which only one mineral is present or is sufficiently dominant that it determines the overall hardness.
If a rock has protruding crystals of minerals then you can of course test those by orienting the specimen to make that be the contact surface. It can sometimes help point towards the identity of what rock type you have, but in most cases tells you very little. The situation is very different if you are testing individual minerals, since that’s what the Mohs hardness scale is really designed for.
The same applies to streak testing, but a ceramic tile with an unglazed back is nevertheless a very useful item. You won’t get far in identifying rocks without a good quality magnifying loupe, ideally with multiple lenses for different levels of magnification. Both an ordinary magnet and a powerful ‘rare-earth’ magnet are essentials. A small UV flashlight is also a useful thing to have.
A club-hammer with a selection of chisels would be a good accompaniment and no self-respecting geologist would be seen dead without an “Estwing” geological hammer. The ownership of an Estwing automatically raises the esteem with which one is held in the rockhound world, with consequent privileges as illustrated below.
