Regarding donations you will benefit from guild bonuses - so the higher the guild level and the guild bonus level the higher boost you get to your stats. You will earn more of everything and you get it faster too! Besides that you gain 1 guild honor point (that you can spend in the guild shop) for every 10k gold you donate. A synth scroll costs 2 guild honor points, which is equivalent to 20k gold. This means you pay 5k gold more per scroll (since you can buy 1 scroll for 15k gold in the shop) but at the same time you level the guild. I recommend to buy mostly synth scrolls since you get most value for your gold. Occasionally buy some time skip scrolls and some socketing rods, but as I said focus on the synth scrolls. Do NOT waste guild honor on buying gem boxes, get scrolls instead.
Please be aware that stealing from guild members (garden or raiders) will result in drama. You all know my stance on drama and the lengths I'll go to avoid it.
Happy gaming all!