shawn
Veteran
We all have advice on how you should spend your money. That's life. New or used, full frame or smaller? I ask because I got a Pentax Q-S1 with two autofocus zoom lenses pretty cheap on eBay. It is a star performer and punches well above its weight. It will fit in your pocket. It has auto everything. You can get going with the camera and the two zooms for less that US$300: pentax Q-S1 for sale | eBay And if you want to shoot movies it will do that, too.
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The Qs are great fun. If you don't have the Prime 01 you should grab one.

That has an equivalent of a 40mm f1.9 prime, equivalent of a 23–70mm f2.8-4.5 zoom and a 70–209 mm f2.8 zoom. The M3 setup weighs 801 grams with the meter and Elmar on it. The entire Q setup is 549 grams.
Beware of going down the C-Mount rabbit hole.... then you end up with things like Fuji 2.7mm fisheyes take from security cameras....

and the you realize it is a killer telephoto body thanks to the crop factor..

For the OP though I'd suggest a different tactic... find a used LX100 or LX100II if you can for the right price. Small, light... has from a 24-75 with a M4/3 (ish) sized sensor. Can shoot in a number of different aspect ratios without much change in resolution due to the way it uses the sensor. AF is plenty fast, has traditional controls and can even do macro. You can set it so it resumes at what focal length you left it at so if you want to just shoot as a 35mm FOV you can do that. And then have the other focal lengths if desired all built in without having to carry anything extra.