Many many things bought/added over the years. My top 10 pics of best spent money for the results in the order of my priority...
1.Replaced the absolute abismal OEM mattress.
2. Installed an EMS and 30 amp twist lock entrance eliminating the "mouse hole".
3. A quality water regulator connected to a 10" cartridge style water filter./ Fed via quality 5/8" "Never Kink" brand water holse.
4. Quality dump hoses and carrying tube under the frame.
5. TPMS - TST 507
6. Added a third electric stabilizer that matched the two OEM units. I stalled just forward of front axle.
7. I'll lump these together: Husky 4500 remote controlled power tongue jack, Level UP bluetooth leveling system, Anderson Levelers, X-Chocks, and quality rubber wheel chocks.
8. Replaced all exterior and interior incandescent lamps with LED lamps and or fixtures.
9. Step stabilizers for both steps and folding step platforms for both doors.
10. Telescoping flag pole with mount on the trailer tongue.
The list goes on but this is a start.