My recommendations for how to isolate and triangulate your DNA matches so you can figure out how you match and find your most common recent ancestor.
Please COPY this post because I regularly delete my posts.
1) Upload your RAW DNA file to as many DNA websites as possible. This will cast your net wider so you may find as many matches as possible since you will find matches on one site that are not on another site . Many are free to upload and will offer you basic tools along with matching. I recommend MyHeritage.com, FamilytreeDNA.com, LivingDNA.com, and Gedmatch.com. *23andMe and Ancestry doesn't allow Raw Uploads from other companies but you can upload their raw dna to the other sites.
https://www.genealogyexplained.com/dna-testing/raw-dna-data/
2) Read and study the Leeds Method. This method is going to be your best friend for figuring out who all those matches are.
https://www.danaleeds.com/dna-color-clustering-the-leeds-method-for-easily-visualizing-matches/
Note: some websites have AutoClustering and it can be very helpful but I still recommend you also do a spreadsheet and/or pen and paper in conjunction with this AutoClustering because it gives you more insight into what is going on with the system and you can add matches from other sites.
MyHeritage has AutoCluster under the Tools Menu of the DNA Page (fee may be required) Genetic Affairs also has an AutoCluster https://www.geneticaffairs.com/features-autocluster.html
3) Cross reference your matches between the various sites to which you uploaded your Raw DNA. You will find crossover matches and these matches can help you cluster (Leeds Method) unknown matches you may find.
4) Copy down, screen grab, download, whatever the website allows all your matches because sometimes people remove their DNA or hide it and you want to be able to look back if they do.
5) After you've done the Leeds Method Color Coding you are going to want to quickly see if you can identify the most recent common ancestor (MRCA/CA) for each color cluster. This can be done quickly if you have a match you know such as an Aunt, Grandparent, first cousin etc. Mark down those you are pretty sure you know. Remember DNA doesn't lie and papertrails and trees could be wrong. Also, remember just because you match Aunt Sally it doesn't mean you both share the same 2 MRCA. She might be your half aunt. Also, all the people in the Cluster may share someone much further back, but for now this will help you figure out your paternal and maternal sides and perhaps a cluster of grandparents to work off of during triangulation.
Note: a Shared Common Ancestor isn't an aunt or cousin or your sister. The shared common ancestor is the one person you are both a direct descendant of. The Match's great grandmother might have been your grandfather's aunt but that aunt isn't your shared common ancestor. The common ancestor is the aunts mother and/or father who happens to be your grandfather's grandparent.
6) Next we are going to look at the Color Clusters you can't easily identify who your common ancestor is. This is going to require investigation. DO NOT depend on the match to have a tree for you to look at and DO NOT trust any tree they have is accurate. You are going to have to get every single piece of information you see for each match. You can contact matches and ask for information but I wouldn't count on most people replying or having any useful information for you. Instead you are going to QUICKLY look at their tree, if they have one, and see if you can identify a match. Go through the Color Cluster and quickly see who has trees and if anything jumps out at you. Look for common ancestors, common surnames and area of the world. If you get lucky and someone in an unknown Color Cluster happens to have a match you can easily identify then write it down for that cluster. If they have no match you can QUICKLY, and I mean within a few minutes of looking, then don't spend time trying to locate the common shared ancestor right now.
You want to find the common shared ancestor of the entire Cluster. You DO NOT want to start chasing down individual matches right now. Doing it that way will only lead to frustration if you are dealing with an NPE ( https://dna-explained.com/2019/07/18/concepts-what-are-npes-and-mpes/ ) or a bad papertrail or very distant matches.
7) If you can't quickly identify the Cluster's Common Ancestor now is the time to start a DNA Tree for this cluster. I recommend doing it as a hidden/private tree and starting with anyone who catches your interest in the cluster. Maybe they have a tree you can work with, maybe they are from the same County or Town. Maybe you saw several surnames that you recognize but don't know how they fit you.
8) As I said earlier, you will have to do an investigation. Begin by putting the DNA match in the DNA tree and filling out their family as far back as you can. I recommend trying for 4 generations on all branches just to get a feel for where this family might have been. If you stumble then stop.
Now move onto a second match from this cluster. Add them to the same tree. At this point they will probably be unconnected to the first match. If you happen to locate some matches that are family then by all means add them in. I also recommend putting their centiMorgans (cM) number in the person notes along with what site the match was from and any identifying information they had on their account so you can reference it later.
9) What if the match doesn't have any information and didn't respond to contact? Google what you know. Do they match someone else who would be their mother, child, 1st cousin? Does that other matching person have a name or tree associated with their DNA? Is there an email address you can see? A unique username? Click on the username and see what information the pop-up window has. Is there an age range listed for the match? Write it down.
Google anything you can. See if you can find old Genealogy forum posts with that email. Are they under that username on Ancestry or Familysearch? Once you have a good idea of their name then see if you can find sources for them. Look for Facebook pages where their friends or family are listed; Whitepages with relatives info; Marriage announcements and Obits. It's a puzzle. Unfortunately sometimes a person isn't easily identifiable so you will have to move on.
Eventually you should have several matches in your DNA tree and it will begin to come together where the match may have occured.
10) Use the DNA Relationship Calculator to get a good idea of how these matches match you and each other.
https://dnapainter.com/tools/sharedcmv4
And the Cousin Chart to understand what each one means https://isogg.org/wiki/Cousin
11) Once you get enough people into the DNA Tree a common ancestor should appear. You MAY NOT KNOW how you match that ancestor but that's where triangulation comes in.
https://dna-explained.com/category/triangulation/
12) You now work to figure out how you fit into that common ancestor. Use the DNA Relationship Calculator, Cousin Chart and the What are the Odds Tool (WATO) to get a good idea of the generation where you would fit.
WATO v1 and v2 https://dnapainter.com/tools
This can take time, and a lot of research, so don't expect it to identify all your clusters overnight. Also, remember you may have to wait for additional matches to pop up for it all to fall into place. If you get frustrated then move onto another cluster.
Once you've solved a cluster you can then divide that cluster into further generations for more of a challenge and to advance back another generation.
I know this looks confusing at first but I promise it works! I suggest diving in head first. After a while of working the system it will become second nature.
Good luck and most of all, have fun!