You can donate as much or as little as you like at a time. Here is the amounts you will need to donate in total to get souvenirs:
20 000 -> First souvenir
70 000 -> Second souvenir
200 000 -> Third souvenir
And for v3:
5 000 -> First souvenir
10 000 -> Second souvenir
30 000 -> Third souvenir
