I suggest you look at the Shemot DNA edition of December 2019 (journal of JGSGB).
1) Ancestry is not helpful for DNA analysis - it is best for family trees and it is also the most expensive for DNA. You would have been better off going for either FTDNA, 23andme or My Heritage, which all give you detailed chromosome analysis, without needing to upload to Gedmatch.
2) Size of segment is the thing I look for - and not just one large segment but several of them. Ancestry does not give you that info but the others do. I look for segments above 20cm for closer relationships. That will mean mostly 1st, 2nd, 3rd cousins, and possibly 4th cousins, but nothing above that. 5th cousins to distant cousins are mainly meaningless, as all they mean is that you share a common (much smaller sized) gene and a very far back ancestor with someone of Jewish ancestry in the last few hundred or even thousands of years (as we are all ultimately interrelated).
3) You will be given many 3rd cousins most of which you will never be able to trace. And most of the companies are also very optimistic, and so 3rd cousin may really mean 4th or 5th cousin etc. The real number of actual 3rd cousins is probably less than that given - though you could be interrelated on the same level with several of your own relations, which would up the number of 3rd cousins given.Sometimes you think a relationship is on one side of your family, when in fact it is on another side, or on both sides. Because of all the 1st cousin and uncle-niece marriages etc in enclosed communities, over time, this spiders web is more likely.
4) You need to combine DNA analysis with a paper trail to get any meaning out of it.
5) You need to test many known cousins to get a fuller picture. I now have a network of known family members on all the main testing sites so we can make comparisons. However, as DNA is randomly inherited, you do need to look for common patterns as not all of your relations will share the same set of genes.
6) There will be some who seem to be closely related that you will not be able to find a relationship for by any means - beware false paternities (children outside marriage) ! Or - as I discovered- someone who was a sperm donor in the USA, whose progeny seemed to be related to me.They all had the same name of Weiss - and I could not understand this as I was unaware of anyone called Weiss in my family. Then a US contact told me the origin of this.
7) Although it helps to look for ancestors having the same origin in Eastern Europe or elsewhere, you may also need to look wider. As my ancestors from Baltic Europe were going to the UK, France and Sweden, and all points west, in the 1860s and 1870s, others were going south to Belarus or Ukraine at the same time. So you could be closely related to someone with a different European origin, due to when they emigrated and where they emigrated to (which could be more than once).
Jill Whitehead, Surrey, Uk
On FTDNA, 23andme, Ancestry, MyHeritage, and Gedmatch