Lately, I keep hearing people talk about block builders, bundles, MEV, and so on.

Honestly, retail investors don't need to treat it as a new profession to study…
I think it's enough to know "how not to get screwed": when you place a trade on a DEX, the transaction isn't immediately on the chain; it might be bundled, front-run, or sandwich attacked in the meantime.
A bundle is just putting several transactions together and inserting them; the usual results are increased slippage, strange transaction prices, or transactions that you click but end up being reverted.

My personal bottom line is three points:
1) For large amounts or new tokens, try to split them into batches; don't go all-in at once and get sandwiched by others.
2) Enable "anti-sandwich/private transaction" features if available (some wallets/aggregators use private channels, at least reducing the chance of being exposed in the mempool).
3) Don't give away slippage settings blindly; it's better to fail and retry, paying the failure fee as tuition rather than getting sandwiched.

Additionally, hardware wallets are out of stock now, and phishing links are rampant…
The more these situations happen, the more you should avoid installing random plugins or clicking on "accelerators/rebates" from suspicious links.
Many so-called "bundling services" are actually just stealing your assets under the guise of helping you bundle.
Take a look.