I understand that you have to grind the game multiple times in order to gain the karma for the higher cost stickers. Maybe this will work:
1. earn your first sticker, usually at 5 karma
2. earn your next sticker for your next 5 karma
3. you can keep both stickers or trade the two stickers (5 karma each) for one sticker worth 10 karma. If you do, remove the two stickers and put the 10 cost sticker
4. keep doing this by gaining 5 karma cost stickers
5. trade them for an equivalent higher cost karma sticker
6. you can get the 50 cost karma sticker by trading a total of 50 lower cost karma stickers you have on your character
I plan to stick the stickers on a thin card board (like an index card) and cut it. then just put a scotch tape at its back to stick it to the character card. that way, removing it is easier and it wont ruin the sticker nor the character card. it will allow re-usability of the stickers in case of a character reset.