Sorry, but without a multimeter (volt/ohm meter) and a test light you really can't check anything electrical.
Cheapest tools that will do the job might only be $15-$25. Harbor Freight even gives away meters as promotional items on occasion, and a test light can be had for $5.
Electricity is invisible, and even connections that LOOK good might be corroded where you can't see & test bad with a meter.
Plug in fuses have small holes at the top where a meter can check for voltage on each side. With one that's not currently carrying power the ohm meter function can test for continuity so you know it WILL carry power when needed. (blown can be obvious, broken can be invisible)
Like cans without labels, you don't know what's inside without a way to check.
The real kicker is that if simple tests & substitution of known good parts doesn't tell the tale, a wiring diagram is necessary to figure out the system & trace it for faults.
We've got a couple members with access to such that can often answer specific questions. It takes a while to get that kind of help step by step.
On line tutorials are mentioned here at times on how to use the tools mentioned. We can give some basic pointers on use if the tools are at hand for practical demonstration so you know how they work.
With a meter & test light, checking at the bulb connectors for power/ground can answer whether those circuits are OK or not in a couple minutes. Can't guess without them.
Wish I had better news, guessing & buying parts (even junk yard) can get expensive. Toss in a light switch could fix it, or it might not until a fuse that looked good is replaced. Proverbial crapshoot.
Luck
