Adding a tripwire sequence to a campaign already made

I have a FB ad campaign that I stopped several months ago and have redone the emails and lead magnet. I copied that campaign but now when someone elects to download the lead magnet, they’ll get a thank you page but also the low cost offer. Then they will either be funneled into a thank you for buying nurture campaign into my big offer, OR okay those who didn’t buy the trip wire but go directly into the same nurture campaign.

do I start with a the landing page goal, into an email sequence into a cart then into the nurture sequence? I can’t get a picture of this in my head of where to start. Thank you!