My first go to is masking tape. Wrap tape sticky side out around you fingers and pat the left over glue. It will often be lifted off with the tape. Keep moving the tape to keep a fresh area to contact the glue. It is clean, safe and easy and can be done with the tire on the rim.

If that fails, I have had good results removing gum from labels with these materials:

1. Methyl rubbing alcohol (not isopropyl) Try on a small area first and if it does not work try another.
2. Coleman Lantern Fluid (White gas) - OUTSIDE ONLY away from any flame or spark! Do not risk using petrol or regular gasoline. Both can be harmful to paint or glued joints, so if the rim is painted do not use.
3. WD-40. Most Safe, but leaves a film which must be cleaned off with dish detergent.

#1 and #2 will evaporate quickly alowing you to feel if any sticky is left.

For #1, #2, and #3, remove tires, tube and rim strip FIRST to avoid contamination or potential chemical deterioration. After removal of the glue the rim must be spotless clean or stopping power will be compomised if using rim brakes.

Also, depending on the label and adhesive, you can use a hair dryer and it will often allow the glue to stay on the label as it is removed.

BTW, #2 is great for cleaning chains.