I would pirate the GOTY version

If you don't want to pirate, then I would buy a cheap license key for the GOTY version from a website like G2A
Here is an overview for the DLCs:
- Far Harbor: a DLC in the true sense of the word. It unlocks a new large area, with a good story, choices to make, it gives new armor and weapons. Bring Valentine with you.
- Nuka World: smaller in scope than Far Harbor, but it's a good DLC only if you play an evil character. If you play as a good character, you're done with the main questline in 10 minutes.
- Automatron: a glorified side quest, but good. It lets you build a large variety of cool robots that can be fighting companions or settlers
- Wasteland Workshop and Contraptions Workshop: useful ONLY if you need to build some SPECIFIC things in your settlement
- Vault-Tec Workshop: get only if you intend on spending hours on building a vault, it is actually more difficult than expected connecting all the parts.