[LEAKYSEALS951]

yo 55- just get out and ride it. Unless you want to dump thousands, get back on the old bike to start with. You don't need disc brakes. 23c are fine to start out with. The rims will take wider tires- the limiting factor is squeezing the tires through the brakes and frame/forks.
If a road bike is really old 1970's- 80's, it might have clearance for wider tires- 30, potentially even 32c. About 20 years ago 90's into the 2000's, things got tight and were 23 specific, but I'd bet you could get 25 or possibly 28c's on it.

One saving grace for older bikes is the rims are narrow (like 14-16mm wide internal width)- which pinches most modern tires down a bit in width- so a 28c will measure more like a 25 width. My 25 conti 5000's measure 23mm on my older rims. The 30's fit more like a 28mm. This makes sizing a little hit or miss, but they will work. 32c measures about 30 iirc on the narrow rims. I run a 38c on a 14mm internal width rim and it works awesome for gravel, and measures about a 35c, and I was kicking the millenial "rapha" crowd's ass this summer.

The nicest thing about the wider tires is you can hit gravel/rough stuff with a lot more confidence and lower the pressure for a smoother ride. Even with 23c, you can drop the pressure a bit and be fine. I run my 23c about 85-90 lbs. Even back in the day I just inflated them to 100 and rode it for a month or two before checking pressure again. No need for 120.

Some of the best bargains going are 2010-2015 era road bikes. Incredible top of the line stuff going for hundreds of dollars because they aren't "disc brake/wide tire" trendy. You can get some REALLY good stuff for cheap.

I'm gonna ride in WV tomorrow- first big ride since breaking my leg. Should be good!