Consider the specific electrical problems you're chasing. Are they mostly sensor and code related, or are you dealing with old wiring and bad grounds a scanner can't see? A good multimeter is essential for voltage drops and continuity, which cause many gremlins. The real question is whether your time spent guessing is worth more than the tool's price.

Ever notice how we get sold on the idea that everything has to be premium to be good? Like fresh herbs, fancy olive oil, or single origin coffee. A lot of it is just marketing. Dried thyme and rosemary hold up great in soups and roasts. Bay leaves are always dried anyway. The cheap jar of Italian seasoning makes decent garlic bread. Sometimes the basic version does the job just fine and we're paying for the story.

Sounds like you gave up way too fast. A gray layer is just hooch and a flat starter is normal after a week. You probably just needed to feed it for a few more days to wake the yeast back up. Starters are way harder to kill than people think. I've brought back ones left for months in the fridge. Tossing it was a waste of good flour.