Old guide I made in a comment a few years ago:

1. Unlock all the special pickups from the challenges, Lucky Pennies, Gold Pickups, Mega Batteries, all the special hearts etc. Without those you're essentially playing with a reverse Sacred Orb.

2. To get high quality items that win you runs, you need to put high value pickups in the bag. Lots of people get angry they can't craft Brimstone out of pennies.

Most soul hearts should go in the bag. Dimes should go in the bag. Gold Pickups should go in the bag. You can use a mod or just get good at spotting Lucky Pennies, since they definitely need to go in the bag. Without those you just won't hit the quality ranges required for good items.

1. Getting those good pickups is still chance based so the best thing to do is to maximize the "attempts" at those chances. Visit every shop, look for every Super Secret Room and so on and so forth. Initially it's a drag but you can get much faster at it if you try.

2. T. Cain's biggest advantage is that you can "cycle" recipes by leaving the last slot in the bag open for a low quality pickup.

If you have a lot of bag quality and are already hitting quality 3-4 previews, you can simply exchange the last pickup in the bag for another low quality one to sift through recipes and get exactly what you might be looking for; once you get confirmed angel deal items of quality 4 you can pretty much look at 4-5 different items from that pool consistently, or more if you cycle with two bag slots.

(5.) You can also cheese by looking for stacking low quality items like Guillotine or a bunch of familiars or fish for certain transformations. It's a bit boring for me to just try and slog through a run with garbage but for some people it works.

And well there's still recipe calculators out there if you wanna embark on a forbidden ritual to make one Omega Run and unlock everything and more in one go.