I've put stars next to each faction to arrange them in priority for myself. I've also used square brackets to denote completeness / not going to expand further at this point in time.
Emperor’s Children. I have secretly coveted collecting a small detachment for a long while. So much so, that this will be my next pet project! Surprise! Top priority! ⭐️⭐️⭐️⭐️⭐️
Iron Warriors. One of my main army collections. Not as extensive as my Alpha Legion by any means, but loving them all the same. Very happy with this legion! Not looking to expand at the moment, but will consider it. I am content with the army as it stands right now, but I do need to paint up what I have assembled. [⭐️⭐️⭐️⭐️⭐️]
White Scars. I don’t own any and I have no plans to own any either. Not a priority, but not ruling them out in the future either. I also find white a tough colour to paint. Low to zero priority overall.⭐️
Space Wolves. I like the fluff and the miniatures, but once again I don’t own any and have no plans for even an allied detachment. Maybe one day a small detachment to "look after" the loyalty of my Alpha Legion? Zero priority. ⭐️
Imperial Fists. They just don’t speak to me. Sorry folks! Don't hate me! Zero priority. ⭐️
Night Lords. I’m not a big fan. I’m not opposed either. Just can’t see me collecting them right now. Low priority. ⭐️⭐️
Blood Angels. I like their vibe. I like how they play. But they are a low priority for me. ⭐️⭐️
Iron Hands. I own small numbers of these as part of my shattered legions collection. There’s a possibility to expand, but I need to complete the ones I have so it is only a medium priority to expand, but a relatively high priority to complete the ones I have. ⭐️⭐️⭐️
Ultramarines. Far too vanilla for me due to 40k, but I do like the rules. Zero priority. ⭐️
Death Guard. I collected this legion in 40k as a main army. But I haven’t bothered with them in 30k. Maybe one day. Medium to low priority. ⭐️⭐️⭐️
Sons of Horus. Lots of traitor players (rightly) love them. But for me I’ve seen them all on the battlefield and internet already. Except maybe for having Horus himself, its a zero priority for me. ⭐️
Word Bearers. I have a bit of a love-hate thing for them. I have a good detachment of Gal Vorbak going that I’d like to round out with Tal one day. High priority for Tal alone. ⭐️⭐️⭐️⭐️⭐️
Salamanders. I have a detachment as part of my shattered legions. I’m complete with them for now. [⭐️⭐️⭐️⭐️⭐️]
Raven Guard. Same as the Salamanders. Love the shattered legion detachment I own. I also have an unpainted Corax yet to complete. [⭐️⭐️⭐️⭐️⭐️]
Alpha Legion. My main army that I’ve never stopped expanding since first edition. Always a priority, but I’m largely done unless there’s a cool new release or I see an opportunity for something interesting or a conversion. [⭐️⭐️⭐️⭐️⭐️]
Knights. Who doesn’t love knights?! High priority to complete at least the Lancer and a couple of armigers! ⭐️⭐️⭐️⭐️⭐️
Titans. No more at the present time, but love the ones I own. One day I’d like to at least consider buying more… i.e., a Warlord! Just not right now. Some lame excuse about saving up. ⭐️⭐️
Daemons. One of my main 40k armies. They’ve translated well to 30k, but I don’t feel the need to expand here or do anything with them other than summoning some occasionally?!. [⭐️]
Imperial Army. Not my thing. Unless serving the Alpha Legion? Zero priority. ⭐️
Custodes. I have a few. I might get a few more. But honestly not my play style or favoured paint scheme either. Low priority. ⭐️⭐️
Sisters. I’d actually like to have them! I have zero. So I’m not starting on them. Tough! Unless I win the lottery and retire early. ⭐️
Assassins and Agents. Would seriously consider this. ⭐️⭐️⭐️⭐️