Opinion

What pack to choose depends on what gameplay interests you

• Horse Ranch: playing with horses is fun but a very specific focus. If you like caring for animals this is definitely a good pack
• Growing together: great for family gameplay. This is one of those DLC that are more in the back ground and can be felt in small details, rather than obvious in-your-face gameplay. It makes infants more fun but also very challenging.
• High school years: Great build and buy objects but I don't like the gameplay. I hate the fact that you can't turn of body hair growth and the social bunny on a global level. It has to be done for each sims seperately
• Seasons: great basic gameplay. The holidays and weather really give a sense of time passing in your game. I consider this pack rather essential
• Get To Work: Despite being the oldest EP, it still has great things to offer. The retail option is very useful to set up stores that can sell almost anything and remain (Businesses and hobbies is more limited for sales). I also like the science career and the aliens but know some simmers don't
• Discover University: Studying is quite challenging if you take 3 or 4 courses a week. But I enjoy it. The flexibility to attend university whereever you live, in any world, allows to combine this with playing a family. The 3 new careers and the robots are nice to have as wel.

Personally I would choose Seasons or Growing together first because their gameplay can be seen in everyday life of every family you play. Horse Ranch, Get to Work and Discorver university require you to actively seek out the game play but they are fun to play if you are interested in their theme. High school years is one of the few packs I regret buying so won't be recommending that one but I know some simmers like it.