@Robinowitz, a voice from your past is knocking with some thoughts for you to ponder about DIY. There are eight million stories in the Naked City, and many times that many in the world of vaping. This will be just one of them. But do your own homework to make the right decisions that you can live with.
After three days and nights of researching DIY in early 2013 I ordered my first "mods", and that same day lab equipment. bottles, etc, base ingredients (PG & VG), and 75 flavor concentrates because commercial e-liquids back then all contained at least 6mg/ml nicotine that I did not need or want because I was not addicted to it. But most of the 75 concentrates were a fail because I missed that day in class when it was said not to assume that because you like to eat something does not mean that you will like to vape it. Biggest fail for me was the fruits and any others that were overly sweet. I learned each flavor by itself first, then found what flvor(s) complimented each one. Then eventually up to 3-4 or more that worked well together for me. In the end I made ALL of my own recipes, I didn't copy those of others, and had over 160 of them by the time I stopped vaping... savory plants (not tobacco) and drinks (alcoholic and not) mostly that were perfect for my tastes in the gear i ran them in. You have years of using commercial e-liquids so know what you like to vape (fruits, desserts, bakery, savory, drinks, etc, etc, etc) and that would be a great place to start from.
Lots of the old concentrates I used are no longer available from their manufacturers. I knew they were going to be discontinued so bought a lifetime supply of them. But I have not had any dealing with DIY vendors for going on 2 years, so the good folks here will have more current knowledge about them. I mostly bought from One Shot DIY Shop and Bull City for concentrates as they had many different brands in stock that I used, and I got my PG/VG from Nude Nicotine.
Methods is another story in DIY. In my case from what worked at first (shake and wait and wait, and...) other methods to what worked the best for me the last years. I mixed by weight, used a magnetic stir plate and I made my own One Shots that all cut the time way, way, way down from mixing to ready to vape. Only took a few minutes to make a batch then a short ride on the plate. A bonus was almost no clean up of equipment either.
Good luck and have fun as you find your way thru the DIY jungle Reonaut.