Perhaps get in touch with the people behind SwiNOG? https://www.swinog.ch/ (Swiss Network Operators Group)

It does seem easiest to start with an IX, where you can follow the published rules to join the IX and connection your network to it’s without bothering every other member.

One may have a good chance talking to people behind projects like https://www.community-ix.net/ and good old in-person networking in places like RIPE meetings. Basically everyone there including people working for large telcos have a personal interest in supporting independent structures.

If you want someone to bounce ideas off of, I've been involved in that space for a very long time and could probably answer a lot of questions with real world experience, regardless of the technology used.

If you have serious intentions of starting an ISP, I'd recommend beginning conversations with a few transit providers right away, feeling out rates and commit terms. Armed with some market info and contacts there, start to look at v4 auctions via [0] or similar so you can jump the line, though you'll have to pay for the privilege. You probably won't be able to transfer blocks into your org until you have commits from one or more upstreams (I know ARIN, and I'm assuming you're in north america, has some more stringent reqs in terms of overall usage within a specified time period, so choose the auction size appropriately [1]). You may also want to consider taking a block from your transit, they will often reassign a small prefix out of their larger holdings for customer use. You can often use that as justification for transferring future blocks.

After transit, start to look at facilities to host your equipment, 'cause you'll need to demarc somewhere and hand off to your transit as well.

Lots and lots of details to get right, but I personally think it's a lot of fun.

[0] https://auctions.ipv4.global/

[1] https://www.arin.net/participate/policy/nrpm/#eight5