I find that buying packs when they are 50% off is way cheaper than buying them in a bundle. Also, I'd suggest to buy the packs you're interested in over a period of time, rather than all all the same time, starting with the ones you feel pretty sure you will like and will bring the most fun content for you to play with.
My first purchase immediately after I got the base game was a bundle consisting of Season, Snowy Escape and Nifty Knitting. It was a great combination in my experience because they really go very well with each other.
Here is my very personal ranking of the packs you are considering buying:
1. Cottage Living
2. Snowy Escape
3. Get Together
4. Parenthood (Game pack)
5. Discover University
6. City Living
7. Tiny Living (Stuff pack)
Cottage Living gets a first place for me, but that's because even before it was announced, I was already playing farming and creating cottages. So It was a must for me. The world is very pretty and quaint, and if you like the countryside you'll fall in love with it. If you don't like the countryside and prefer more urban settings, it might be boring to you. There's a lot of gameplay revolving around farming, raising animals, interacting with small wild creatures, living in a close-knitted community, etc. If these things are appealing to you, go for it! :-)
I put Snow Escape in 2nd position. I really like the world (Mt Komorebi) and the winter sports skills (snowboarding, skiing, mountain climbing). The world is very charming to explore, including all the hikes and the fact you can swim in the river. I love mountain climbing expeditions. I don't care about the festivals.
Get Together is technically all about clubs, but this is in fact a feature I don't really care very much about. What I love about this pack is the new world, Windenburg - which is absolutely my favourite one. It's the most European of all the Sims worlds and it's pretty fabulous and unique. I love the build-mode items. In spite of my underuse of the clubs system, they have a lot of potential and really enrich the game.
Parenthood is very good if you enjoy playing families, because it enriches interactions between parents and children. It turned children and teens into more interesting Sims to play, for me. Prior to buying this pack I never played kids because they weren't as interesting as young adults. But this pack adds some special new elements such as character values that can be developed, and I really like that feature, as it contributes to developing Sims with more defined personalities.
Discover University is another pack that brings a very beautiful world. I don't care too much about sending my Sims to University, as sometimes the gameplay involved in earning a degree gets really boring, but I do love the world. In fact I've pretty much removed all prebuilt lots and I've filled it with buildings that have nothing to do with university and I use it as a normal world.
City Living: I'm not a huge fan of this pack. I don't particularly like the new world and I don't care about the festivals. But you might like it more than I do if you prefer an urban setting to the more common suburban setting of the other worlds. It also features apartments.
Tiny Living: I like the concept but I rarely, if ever, use content from this pack.
