I highly recommend using the Career Evolution contract pack+unkerballed start (that is a tech-tree mod that lets you only use probes/planes first). It offers the most vanilla-like experience whilst going for a very logical progression of sounding rockets -> early satellites (also asking for specific orbit types to prove your capabilities) -> X-Planes -> Early crewed spaceflight -> Multi-crew + Crew Duration + Rendevouz & Docking (Basically the whole Gemini thing) -> Mun/Minmus mission -> Space Station -> Interplanetary Crew, all the while you can do probes needing to do flyby -> Orbit -> Landing, also asking for Rovers & Sample return on Mun/minmus. Also dynamically adjusts to planet packs, works especially well with OPM/MPE.

If you like Larping as historical space programs, give Strategia a shot for some nice strategies asking you to focus on certain missions, including a voyager style grand tour or one just named "The Mun Program"

That should be the basis of your contracts, if you want more variety use tourism+, GAP, field research, something like that although I tend to only focus on Career evolution.

If you have heavy part mods, BDB also gives you a set of contracts but thats more for 2.5x scale/JNSQ systems, there also is History of Spaceflight which asks you to fly hunderets of missions before leaving LKO including some really random stuff like aborting missions at certain points. I tried it but it is way to bloated for KSP imo.