I defintely reccomend waiting for sales to get your packs since they do go on sale fairly frequently. But here's how I would rate the ones you're considering.
Get Together - I agree with others that the club system is defintely useful and can come in handy. And the world is really beautiful, with a bunch of unique lots. (I love the Bluffs and Chalet Gardens) but other than the club system, most of the gameplay (and even CAS items) is centered around partying/nightclubs/etc. So if that's not your kind of scene (I'm not sure where you're from if there is all ages clubs or not) then maybe you should consider one of the other ones for now. It's defintely a pack I think is worth buying though.
Snowy Escape - Whether or not you'll like this pack probably depends on whether you like sending your sims to do outdoor sports or hiking and things like that. I really like the Lifestyles feature and the world is super pretty and unique. The pack seems to be very well made in my opinion. And the Build/Buy items are some of my favorites. (Lots of kitty cat items.) And although Seasons isn't even required to have the snow and weather, I think you'll get more out if it since you do have that pack. Plus, since it's post-Island Living the water is swimmable.
Discover University - I was struggling whether to put this pack third or fourth (the toss up being City Living). What I'll say is... if you're not into playing school/university/sending your sims to class, it doesn't really offer a whole lot in terms of gameplay. But this pack has some of the best CAS options in my opinion, and the BEST out of your options. I find myself using so many of the items all of the time. They are extremely versatile. And like with Snowy Escape, the water is swimmable. And these last 2 reasons are really why it beats City Living for me personally.
City Living - Don't get me wrong, the pack is defintely fun with the festivals and what not, but since I myself didn't grow up in, or even near any major cities I don't really feel a super strong connection with it, or San Myshuno, compared to Cats & Dogs, and Realm of Magic which has a sort of small town vibe.
Tiny Living (Stuff pack) - I was prginally going to rate this one lower since as a stuff pack, it doesn't really offer much gameplay apart from the tiny home lot, but the items that come in the pack are super cute and can really come in handy when you're cramped for space.
Parenthood (Game pack) - I'm probably in the minority here, but Parenthood is probably one of my least favorite packs. If you're someone who enjoys playing with families it may be of interest to you. But if you're not a family player (like me) then it doesn't really offer much. Like the name suggests, it's all about raising kids and parenting.
* I don't have Cottage Living yet, so I can't give any opinions on that one.
And now even though these weren't on your list, I'd still reccommend these two.
Vampires - If you enjoy supernatural/occult gameplay, this pack is an absoulte MUST HAVE. It's easily one of my top 3 packs (along with Realm of Magic and Cats & Dogs) since I am majorly into this play style, and although it's not super versatile, the CAS really comes in handy if you're making goth/punk sims or want some victorian-era style clothing for whatever reason. The only dissapointment for me with this pack is like with Glimmerbrook, Forgotten Hollow is so small, and I really wish there were more lots.
Paranormal Stuff Pack - Again, this is one you'd only want to consider if you actually like occult themes, but this is another one of my favorite packs. And one of the few stuff packs I feel that's actually worth the full price, since it introduces a lot of gameplay for its price point and feels almost like a mini gamepack. It doesn't actually come with any new occult lifestates (since ghosts are base game) but defintely ties in nicely with the other occult packs, especially Realm of Magic! And it's also the only stuff pack that comes with new NPCs (although you do need to summon them.)
