If your L3902 has the turnbuckle style lift arm stabilizers get a 24mm open end wrench. A larger/longer adjustable wrench can be hard to get in and on the turnbuckle jam nut depending on what tires your running. I have R4's on my L2501 with no spacers and it gets really tight on space.
I know the top link adjustment jam nut is larger than 24mm but I use my adjustable wrench for that one. It is easy to access.
The category 1 lift arm pins on one of my implements uses a 1 3/8 inch imperial nut to secure to the implement. I had to buy a 1 3/8" deep well six point socket 1/2 inch drive for that one. The nut is recessed in the frame work and not accessible with a box end wrench etc.
Other than that a normal set of 3/8 and 1/2 metric sockets and set of combination wrenches should cover 90% of fasteners for normal adjustments, maintenance etc.