I have been trying for three years. I live in the mid atlantic, and am in a community garden. Ever year, they are unhappy, but get decimated by bugs. I grow long island improved from seed. I start them in March at home. They grow, I spray with bbt and with neem. The bugs win. Wrong seed? Another cultivar? Give and focus on the attainable, or try again

What "bugs" are you talking about? Slugs and cutworms destroying the seedlings? Cabbage butterfly caterpillars (aka cabbageworms) feasting on the leaves?
The best defense against the former is to fit the seedlings with protective collars: you can buy them or DIY. Sand, wood ash etc work just as well but the big problem is the moment they get wet they become useless: that's why the collars.
The best defense against the latter is vigilance and intervene the minute you spot the first caterpillars or eggs appear. Leave neem to the snake oil salesman: if you want to use Bacillus thuringiensis, make sure it's the aizawai variety (IE Sumitomo Xentari). Cabbageworms, very much like armyworms, have very high resistance to var. kurstaaki, so aizawai should be used instead. Alternatively imidacloprid will make short work of them.

There's also the question of "unhappy".
Brussel sprouts are generally grown as a late Fall crop: generally speaking here (USDA 7b) they are sown in July and planted in late August/early September. Like other members of their family they don't like too hot of a weather and prefer cooler nights.
Finally there's the big mistake we all commit when starting out with cabbages and their: they are among the most nutrient heavy crops, meaning they need to be heavily fertilized. By "heavily" I mean a lot of fertilizer before planting, more at transplant and then even more every 30 days. There's a good reason an old saying went "cabbages only grow well near the graveyard".
Brussel sprouts and cauliflowers are the most-nutrient heavy of the family so be warned.

Concur: Timing is critical with Brussel Sprouts. They do best as a fall crop in higher zones. They are are insect magnets so you will have to wage war on those. They will stand freezes so in 7a plant for harvest in late November- December. Top the plant when sprouts appear on the lower stalk.

Hi "neighbor!"
Great advice already.

Johnny's seeds has a good article about how critical (iffy) the timing can be with brassicas. You might find new seedlings ready at the nursery about now though, for a fall crop. I was thinking about it.

Good to know about the heavy feeding! Something I usually neglect.

around here it is cabbage worms (two kinds) and harlequin bugs and maybe whiteflies that destroy my brassicas. I use Bt on the worms (no risk to bees or parasitic wasps) and am using Spinosad on harlequin bugs and ?whiteflies this year.
I did see lots of cocoons from parasitic wasps. I grew a few different brassicas and saw a preference of the caterpillars liking one more than another. You might be able to leave caterpillars eating collards or flat red russian kale (seemed their favorites) to support parasitic wasps and protect your brussels sprouts carefully.