My advice would be to go easy on packs and get to know the base game first before adding to it. Get a feeling for this version of the game, find out what you like most. Is it building, playing, creating Sims in CAS. Find out what you miss most in your game and go for that. I would start with just the base game or maybe one or two packs.
If you want a pack to start I would recommend seasons as a starting EP and perhaps an EP that adds a world/more lots in a world that appeals to you personally.
Wait for a sale, especially for bigger packs. That really helps if you want to get more of your money.
