Bit new myself take it with a small grain of salt. But I suggest to look into what things does though. It'l help you in the long run.
Though Skaven are a bit devided
atm with if you want a bit of everything you go Chaos Alliance. You could also go full on Pestilens, Skryre to reap the benefits there with a bit of room for allies.
I like Verminus and would probably go with that. Though the isle of blood set isn't made anymore? It would give great vallue, as does the pestilens start collecting set.
Pestilens:
Congregation of Filth (140 points). You can grow this into a Virulent Procession later on.
Pestilens beginners set.
1 plagueclaw catapult (180 points)
20 monks (140 points)
1 Plague furnace (200 points)
ad another 20 plague monks if youd like to get Congregation of Filth. Or 40 for (240 points)
1 more plague priest. (80 points)
Wich will be around (980) points alltogether if you go with the 40 extra plaguemonks.
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As for when you have the Isle of blood set. It will be a Chaos Alliance.
Isle of blood set.
1 warlord (100 points)
1 Warlock engineer (100 points)
1 packmaster (80 points)
2 ogors (120 points)
2 x 20 clanrats (240 points)
Wich is 770 points. From wich you can go to allot of diffrent things. You can ad some ogors, increase the numbers of clanrats or ad other units.
20x Stormvermin for example are (280 points)
Wich means you will have to get rid of a weapon team or a packmaster if you ad these. But this list has a bit more options. I'd suggest just looking at what you want from an army and what you want from a skaven army specificly. These are just examples. I myself am slightly new to
AOS and this hobby myself. But there are some fun things you can do with skaven.
Since not all skaven clans got batallions unlike Pestilence and Skryre. You can just go chaos Allegiance and pick what you think would fit. Still I doubt people will hack your head of to put it on a silver platter if you slightly go over 1000 points.
Also this site might help you make a list. Know that there are little details and you will have to search them up :
https://www.warhammer-community.com/warscroll-builder/. Its from
GW themselves.