Your question is a little vague. What lego themes are you most into, and what is your budget limit? That would greatly help narrow it down.

If you like modular sets, I'd get the Police Station. It's on the "Last chance to buy" list as it's retiring really soon, and modulars get really expensive once they retire.

If you like car build the ecto-1 is great

Buy sets you like. Build MOCs and scenery to link them together. Profit.

Give up on a perfect display idea unless you build your own. Just allow it to be cool things you like and don't worry too hard - it's Lego, you can always change it.

If price and space aren’t limited, the modular city sets are the gold standard. Stuff like the Natural History Museum, Jazz Club, even Avengers Tower are designed to link together for a cohesive city street.

For castle stuff, Lion Knight’s Castle and Medieval Town Square don’t directly link, but share a lot of design elements so they look nice together.

The ninjago city sets

The new Lego Harry Potter Hogwarts Castle set 76435 is a modular, and will likely have a dozen sets that all combine into a large castle. It’s their third iteration of this framework - so far it looks pretty good!

https://preview.redd.it/lvhkbph21bcd1.png?width=1584&format=png&auto=webp&s=b4f95ea0cf7804ccf49c9cb9ba55e7a37c8270a5

The obvious answer is the modular town buildings, because they are designed to all clip together and make a street.

Vehicles will always look good displayed together, as each is complete and self contained. I like the larger creator expert vehicles, but the speed champions are also great.

There is a new line of 25th anniversary Lego star wars stuff too that are all mini dioramas where the bases are all in a matching style.

Welcome to the addiction. Be careful, you can get into a hell of a backlog really fast.

First tip, determine where and how you will display the sets you collect. Nothing worse than determining you have a perfect spot only to learn later that it's not the right size or that particular display stand is no longer in production, etc. Also, don't display in front of windows unless they have UV protection in/on them.

2nd tip, buy the sets that are about to retire from LEGO, before they retire. HP doesn't jump a ton in price after retirement, but they will be more expensive, especially the further from retired they become.

3rd tip, check out bricklink.com for all your lego needs. The site is clunky and not very user fri3ndly, but you can score some deals there for sure. Especially if you're looking for a certain figure, and not the whole settled came in.

4th tip, be patient in buying retired sets too. If you're patient. You can often find a better price from another seller, or you can find a lot with more than one set in it for example, I got pretty much the full 2018 wave, with boxes, for $150. They are used and need dusting and rebuilding. But the price is so good I couldn't pass it up. I have all these sets already, but having spare parts is never a bad thing.

5th tip, Check out rebrickable.com for alternative building directions. Lots of people design instructions for a wide variety of builds and you can buy the instructions from th3m to utilize your own parts for building. I know you said you just got into LEGO, so your misc parts won't be much, but you can see some of the build designs that you may want to do later on, and then search out the sets that go into that build.

6th tip, have way to much fun. Watch the films while you build. Take your time with each bag. Make little scenes in each build too. Dont be scared to make it your own style too. Move parts around. Switch figures with other sections. Etc.

Fun fact about your first set, it’s the most complete Hogwarts in LEGO form we’ve gotten so far.

Welcome! I really enjoyed building the Diagon Alley set. And this Micro scale of Hogwarts too.

One of us!

This set surprised me. I had the large collectors castle but it was so big. Still a fun build. I got this as a present and ended up selling my larger set. I think this looks so nice and so many Easter eggs and looks great. And displays easier!

I am looking to get the micro diagon alley soon as well. The large Diagon Alley set is also amazing.

The new Burrow is a great set! I had the previous one and the new one clears for me.

I would just like to see a few minifigures in the beautiful gardens. I really like the sets and hope there will be many more.

Hey thank you all for responding!!! I concur that it's ultimately just what I decide, so I'll let you know my pre-picked answer once the voting is up...... Feel free to just guess what you think I'd choose..... Hints are offered if requested

You should collect the ones you like.. Not whats most popular on reddit.

Currently, sets with the Forbidden Five (except Drix and Nokt) are your best bet. With one exception, I think the cheapest way to get any of the other Five is a $75 set. Kur is exclusive to a $110 set right now, Rox an overpriced and hayed $75 set, and Zarkt is in a $40 set, but nothing else he comes in is cheap. Besides this, any Tournament Temple City and Temple Bounty exclusives are worth a lot, as any big set exclusives tend to be.

Sounds like it’s time for the Eiffel Tower

Alien Conquest's Earth Defense HQ will never be dethroned.

Medieval Market Village, Parisian Restaurant and the first VW camper are all tops, but the Earth Defense HQ is my all-time favorite. Solid set for play or display, including an excellent Vic Viper. To me it's like the point where Classic Space met modern design in one of the most substantial $100 sets ever.

I really enjoyed building the new Land Rover defender set

The small tumbler, speed champions jesko, Tron light cycles, and the DC CMF series.

Scooby doo mystery machine

the medieval blacksmith is my favorite current set they’ve put out, otherwise the original death star

Inquisitor shuttle is a fantastic build, the downside is at a glance it’s just a black slab, but when you actually look at it properly it is a really great set

The starship collection or dioramas are great for display. I mean you can display any of the sets I just find playsets usually have interiors and extras that you don’t display. That being said I have a room full of playsets on display. lol. If you have space UCS sets are awesome displays.

Jangos Slave 1! Best build I’ve done so far and fits perfect if you get kenobis star fighter which is only $25 bucks

https://preview.redd.it/7hdncc4sq64f1.jpeg?width=4032&format=pjpg&auto=webp&s=00886517822b1c30fa9c6158712b3246f0f468cd

I have a tie fighter, interceptor, and bomber. As well as the Executor and the Invisible Hand on their display stands. The Mandalorian’s N1 starfighter is making an appearance in the background.