The Ram schedule of service is a good one to follow. You can always do extra service if something seems off, some work may make sense based on use or misuse.
I am a big supporter of replacing belts, hoses, and timing chain/belt at about 125 to 150k miles especially if run in extreme environment or over a really long period of time. No reason, just to save me some hassle in the middle of nowhere at an inconvenient time. Other things I replace when they need it due to a known and verified problem, such as brakes, tires, wipers, and other things. Fluids I change at factory intervals when under normal use.
I wouldn't throw a ton of money into a vehicle unless you either have a ton and nothing to do with it, or you verified problems. Sometimes you can cause problems instead of preventing. I changed transmission oil one time because I thought it should be done (not in schedule at that time) and it slipped after like crazy. Took a while to screen out contaminates that had dislodged post change.
Good luck.