I think the location and what type of house you are buying depends on the repairs/improvements. Also who your target renters are.
I personally specialize in buying older homes 1900-1970 and get them fixed up to the point where they look nice. I rent to people that want a B grade rental and have pets.
I paint the walls but I don' t replace the paneling with drywall.
I rip out bad kitchen cabinets but I replace them with craigslist used ones
I leave in old carpet if it is still in good shape but not a nice color. Great for people with pets since they trash carpet faster due to accidents. I tell them up front the replacement cost is next to zero for the original carpet.
Also a lot of the older homes use real lumber for the floors since plywood did not exist yet. I paint or stain the wood to get hardwood floors in my home. Takes less than 40 dollars to do a room and under an hour so scratches and stains don't bother me.
I avoid
Garbage disposals. Constant repair calls on them
Bi-fold doors (half are garbage when a tenant leaves after a year)
Sliding screen doors (tenants wreck these constantly)
I rent my units 25-50 dollars less than market (hard to tell since I have mine in small rural towns). I have never needed to run a facebook listing for more than 30 hours to get 10 plus people interested in it and rented out.