Some wide ranging thoughts here.
1. Don’t worry about the 50 hours XC. You can probably knock that out during training.
2. Don’t expect the 15 hours of CFII to be all that’s needed with a CFII.
3. What you can do now is fly cross countries for the $100 burger. Use flight following, go to towered fields, get used to the comms of being in the system. The instrument rating is about being able to channelize your attention very granularly.
4. While you’re flying the burger runs, hold yourself to ACS standards for the Instrument rating. Heading, airspeed, altitude, climbs, descents. Start working thru descent planning, using the checklist. Get ahead of the flight by getting destination weather as soon as possible. Write down ATC instructions, follow them.
5. Don’t try to fly under the hood before your CFII says you’re ready to do it with a safety pilot.
6. The knowledge component is a like trying to fill the Grand Canyon; the rating encompasses instrument knowledge and procedures applicable from the Private to ATP certificate. Don’t try to memorize the knowledge, learn it’s applicability in practice.
6. You need to understand you’ll learn as much about weather as you will about instrument flying. Weether Flying by Buck and Buck should be a prerequisite before starting any instrument ground school.
7. Flying backseat with your training parter will be eye-opening.
8. Don’t rush it.
9. Get actual. If your CFII won’t do actual, find a different CFI.
10. Whatever you do, don’t think this will be easy. The flying isn’t that hard, but putting together everything to safely fly in the weather is the challenge.