Been playing this server for a year now and I never donated for anything. Donation items aren't exactly donation-only items. My best advice to you is to make use of economy manipulating strategies like making a good trade connection with other traders, go lowball with prices when buying then sell high. Sell stuff that are in demand, as well as stuff people don't usually sell but still has high demand. I for one have basically low merchant skills in my RO history, but I did just fine. And of course, don't forget to make friends. This game is best enjoyed with the company of good friends.
It took me at least a month to get half decent, and that's because I'm a lazy bum. 2 months of casual playing (and friend searching) and I had my own set of donation items + cards.
1. Hunt for zeny (gold drops aren't that modified in gld_dun03, there's also a lot of loot in for_fild02). Buy donation coupons.
2. Farm the ff:
a. Yggdrasilberry
b. Deadly poison bottles
c. box of storms/cursed water/converters
d. glistening coat
e. speed potions from the turbo room (my friend R e i n made a fortune out of it)
f. work on getting a dungeon pass (allows you to access a dungeon with a better ygg spawn than the for_fild02 map)
g. quest items which are always bought in bulk
3. MVP summoning using Abracadabra/MVP hunting with friends - it yields good harvest of MVP cards if you're patient enough.
4. Join events
5. Last but not the least, don't be afraid to take risks and mingle with people. Hold good conversations with them and most people would be glad to help you out. If you need more help, feel free to ask me about it.
EDIT: and oh, it does feel like a low rate with high rate features. Character building takes major brains, but donating is not mandatory to win. I assure you, rumors are just rumors. Donating doesn't make you extra leet in this server. Have fun ;D