From my experience getting shards from donating is the best and fastest way to get shards, as long as there is no new tech to spent KP.
With some tactic it is quite easy to get a max out of your KP.
You can donate to every wonder in the world. Not only in the neighbourhood/fellowship.
Wonders in which the owner already spent a lot KP are very good, because you don't need to spent much KP to be safe on a shard reward place.
The first levels of a wonder need less investment to be safe on a shard reward place.
If you are safe -> go on. Sooner or later the wonder will be full, if not you can still come back anytime.
With some economical force (coins/goods for KP) it is sometimes possible to ninja a rerward place for around 30 KP.
For an empty wonder it is easy to calculate the KPs to be safe.
Total KPs needed for the lvl : (places with shards as reward +1)
For example a mountain hall lvl 3:
310 KPs needed for the level, 3 places with shard reward, so it's
1. 310:4 = 77,5 -> with 78 KPs invested and being on first place you will get a shard for sure and can go on to the next wonder.
Firts place is important, because in this calculation we assume that 3 players need to get ahead of you to push you out of a reward place.
To get ahead of you one player needs 79 KP.
3 x 79 = 237
237 + your 78 investment = 315 = impossible, because the wonder level only needs 310 KP.
2. If the owner already spent 40 KPs it gets even better because then it is
(310-40) : (3+1) = 270:4 = 67,5 -> safe with 68 KPs on first place -> go on.
3. If there is a player on first place with let's say 100 kp already you can then calculate
(310-100[KPs already spent from #1]) : (3-1[#1]+1)
= 210: 3 = 70 ->with 70 KP and being on 2nd place you are safe to get a shard
If there is more then one player more donating to the wonder then there are places with shard rewards you can substract their spent KPs too.
So if there are for example 6 players (including you) donating to the lvl 3 mountain hall and the two last players donated 3 and 15 KPs you can subtract 18KPs (3+15) from the level KP for your calculations.
So for the previous examples it's:
1. (310-18) : 4 = 73 KPs on first place to be safe
2. (310-40-18) : 4 = 63 KPs on 1st place to be safe
3. (310-100-18) : 3 = 64 KPs on 2nd place to be safe
With all that in mind you can calculate the minimum required KP to get the max out of your KPs.
For total vacant, or unpopular wonders it might be good to look for some more crowded wonders though, to minimise the risk of being the only donator for a long time.