1. Get Route 10 item
2. Fight Route 10 trainers with leftover PP?
3. Take Lavender Center
4. Equip optimal item for Lavender Rival
5. Fight Lavender Rival
6. Take Lavender Center again
7. Get Route 12 TM 
8. Get Route 12 item
9. Equip optimal item for trainer grind
10. Decide whether to fight Route 10 trainer for Speed EVs/non-Attack EVs (only if close to maxed)
11. Fight Route 8 Lass
12. Withdraw HM friend
13. Get all remaining items
14. Get Tea
15. Check Celadon TMs
16. Deposit HM friend (unless poison risk)
17. Decide whether to fight Level 29 girl or Route 10 trainers
18. Fight remaining Route 10 trainers
19. Fight remaining Route 8 trainers
20. Fight Route 12 trainers