You have some slick moves, @mrpipes!
So there’s a couple different schools of thought about mixing methodology… Weight mixing and volume mixing. While many (most even) tend to gravitate toward weight mixing, @Sprkslfly makes a compelling argument for the Volume Club too. You should hear how both methods go and then decide for yourself which seems to suit you better.
@adary thinks the way I do… Whether I am doing weight or volume, I still mix directly into the bottles rather than using pyrex bits and bobs. It’s just easier for me. So straight away I would recommend getting a number of desired size bottles and eschew the lab gear.
The calculator is of course here on this site. It is comprehensive, intuitive, free to use, and functions quite well. So check that off your list. As for labels, some people use fancy machines, some use Dymo style thermal labels, some use masking tape, etc. For starting out just use masking tape unless you have a labeler already. You can spend for a label maker later if you choose to. Early money is best spent on actual mixing supplies like NIC, VG. PG, concentrates, bottles, scale, syringes…
As for bottles, I wouldn’t get a large quantity of a large assortment. Some smaller ones, maybe 30ml, for testers then some 100ml for known good ones. You can add stock later and adapt as needed. No need to burden yourself with multiple calculations for multiple sizes early on.
Depending on budget and patience level, you can hold off on spending for 3M DIY until later and just use time maturation for now in a dark, cool cave. You can work with advanced maturation procedures like 3M DIY later, once you’re used to mixing and that routine.
As for the concentrates, VG, PG, nic… I would get separate VG and PG so you can dictate the ratios more closely and have more control over that. And PG diluted nic is easier to work with than VG diluted, being thinner. I prefer 100mg because you add less per mix than say 48mg, but I don’t recommend any higher than 100mg (because, danger). As to what flavors you choose, no advice there as that is strictly personal preference. I’d only advise maybe small quantities until you know which ones you like and will use more.
I did not intend for this to be so long, sorry about that. Bottom line (or TL;DR), KISS principle applies when starting out. It is already complicated enough without making it more complicated with a lot of unnecessary variables added in right away.