I like using
Soapers Choice for my oils. You can get castor oil in 7 lb bottles and Coconut oil Organic or not at a good price. They also have numerous other oils too. Yes, you do have to pay shipping, but I found it still cheaper than Costco. They also ship quickly (out of the Chicago area).
I agree with Zing, a good Stick blender that I get at Costco when on sale and a soap cutter that I found on eBay. I would add a scale to measure ingredients, I find it more accurate than Tsp & Cups, with less failing for myself.
Have bought a lot of the other supplies at the dollar store, or Big Lots… Plastic pitcher for the lye water (Label with a sharpie for Lye Only), plastic and metal bowls, spatulas...
As for the Soap Molds, I love the
Essential Depot, Silicone molds, shop their sales. They clean up nice and make it easy to un-mold soap. I started out with homemade wood molds and had to line them. But asked, DH for the silicone mold and I have no regrets. I also get my Lye here too. It's great in soap and also for clean the house drains.