I've been quietly reading in the background and I've talked offline to a couple people that have been hesitant to join in on the Build a Line Challenge. It seems some are over thinking this challenge and it's becoming scary and intimidating.
The line Brenda has/had is great for mass production, so to speak, because they're relatively simple finished pieces all using similar items all in a particular style where she could create a few per hour. You look at her sheet that she's shared (copy below) and they all look close to the same but not quite, they aren't all exact. They are all similar enough that you'd recognize it as her line tho.
If you go to any jewelry store, you see they have similar pieces but not all exact. They offer color choices. Size choices. Slight variations but they look relatively the same. It's that cohesive look.
Don't let the challenge scare you, break the challenge down into baby steps. Gather your pieces for what you have in mind (whether physically or on paper), keep it simple if you're a beginner. Take that piece, make another that uses the same pieces but add variation. Change the colors, change the sizes. Offer "options" whether it's all necklaces or all bracelets that are similar but slightly not. Or offer a set of a necklace, bracelet, earring, ring using the same group of pieces and color scheme so they flow together scaled down to a size that works.
Here's an example of a simple "line" I did and I can expand on them. As you can see, each grouping I used the same piece over and over. I used the same colors over and over. I used the same spectra beads over and over. I mixed them up, mixed and matched, I'm giving the customers options. You don't like pink? Well here, I have red. Oh you don't like warm colors, well look over here, I have cool colors. Oh, not a fan of brass chain, well guess what, I have silver steel chain. I'm doing whatever it takes to reel a customer in, grab their interest, make that sale. Options is key. Retail stores do it, you can see how Brenda does it, you can see how I've been doing it.