Costa Rica travel tips

Hi everyone, I’m planning to visit Costa Rica next December for a 3-week trip, likely from December 13th to January 4th. Do you have any tips for making the most of this beautiful country? I love hiking, adventure, surfing, and road trips. I’m less into luxury experiences, but I wouldn’t mind spending a couple of nights in a nice private Airbnb with a pool. I’d also like to avoid crowds whenever possible. Last but not least: What do you think would be a reasonable budget for a 3-week trip?

Thank you in advance to everyone😊