How impatient are you? With limited funds I would recommend to wait for a sale. EP often go off 50% during a sale so then you could get an additional pack for the same money.
For the rest it depends on what you like
Seasons : gives a general feel of years passing and makes the world alive
Get together is great for the basics. You get a big world with plenty of lots to fill. The club feature allows to easily get together with groups of sims
Growing together and parenthood add more depth for raising families.
Realm of magic, werewolves and vampires are essential for playing occult or fantasy themed stories
Cats and dogs or cottage living are very fun if you like to focus on animals