Look, this is just my two cents for anyone wanting to build a custom bike without obsessing over weight or being a total brand slave. This isn't a check list, just what I’ve learned from building a ton of bikes over the years but I must caveat that the parts I do spend on are almost always odyssey or animal or Merritt.
One thing I always regret is spending big money on seats and posts. Honestly, they’re massively overpriced for what they are especially pivotal seats and posts. You barely spend any time sitting on them anyway. If you just want a plain black seat, save your cash and get a set off aliexpress. there are reputable dealers on there now. Put that money into the parts that actually matter.
Chains are another one. I’ve run KMC for years with zero issues. Most "BMX brands" just mark up KMC chains and put them in a fancy box the Animal Hoder chain is literally a KMC. Buy them from a regular bike shop and save yourself. Same goes for tubes. These BMX companies aren't manufacturers; they’re just brands. Don’t pay extra for a logo on a box when you can just buy Schwalbe, Conti, or bulk 20" tubes for less and get the same thing.
When it comes to headsets and bottom brackets, just buy whatever is cheapest or fits your stack height or bb width. There’s almost zero performance difference unless you’re paying for high-end bearings, and even then, it’s marginal. I usually grab Federal BBs just because they come with those longer 51mm spacers but now that I have the spacers you can just buy built mid bb bearings for replacements.
Now, grips are where a lot of people seem to get a deal on, which is good. You’re holding your bars the entire time you're riding, so comfort matters. I’ve found ODI quality has dipped lately, so I stick to Edwins or Brocs—they last the longest. It's worth getting it right the first time so you aren't stuck swapping them out constantly.
You should also spend the extra bit of cash on your forks and stem. If you’ve ever seen a stem crack or a fork snap, you know how scary that is. Stick to stuff with a solid reputation or what the pros are riding. Bars like forks a lot better than when we were kids most are strong enough for the average rider but pay attention to the knurling. Shoddy knurling means your bars are more likely to slip and may require a bit of post purchase sanding or scoring to get working again.
Aside from a new frame, wheels are the best upgrade you can make. Good rims and hubs last forever if you take care of them. I run a Profile rear hub because I can actually get spare parts for it, which is getting harder to do with other brands. If you don't want to build your own, Odyssey and BSD make the best out-of-the-box completes.
As for cranks and pedals, I don't do pedal grinds or massive drops, so not so concerned about strength. That said, Profile cranks have gotten so expensive lately that they’re probably not worth the jump in price for most people. Most 22mm or 24mm cranks from reputable brands will hold up fine. For pedals, Odyssey and Animal or the Merritt P1s have always been good.
Anyway, that’s where I’m at with it. What do you guys think?