...but based on what I have read and experienced so far, elderberries are fairly easy to grow.
Do you know what kind of soil you have? I spent a modest effort to convert my mostly clay and high pH soil to a low pH loam (mixed/added a peat/potting/organic-rich soil, wood mulch and the native soil on a 1/3, 1/3, 1/3 ratio) and was somewhat militant about watering in the first 3-months (driest part of the year around here).
However, I think the fact that I started with established 2-year old (18-inch high) plants in pots was the biggest contributor to my success.
As far as grafting goes, I'm not sure it is worth it in regards to elderberries, since they are so easy to propagate via cuttings.
See: https://gardening.stackexchange.com/questions/14194/can-i-graft-elderberries-sambucus
Because of the large pith cavity in elderberry stems, grafting is tricky and good grafts are rare. It's better to grow them from cuttings. Spliced side grafting onto one-year-old seedlings may be successful.
The best type of cuttings will be hardwood cuttings taken with a heel. This will help prevent rot from taking over the large vacancy where the pith is, and ruining the cuttings.
I will see how I do this year with the cuttings I currently have in 4-inch peat pots, and make reports/updates here. Maybe my success will be short lived and I'll be in the same boat.
However, if you really like elderberries, I would suggest you try again, in my limited experience they are "easy". Maybe find an existing plant and get a few cuttings. I found the following to be a good guide:
https://www.mommypotamus.com/growing-elderberry/
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