what do you want to know? post.
This is a hard question to answer because it depends upon the ingredient, the product you're making, and how much you'll use the ingredients, but I'll offer a few suggestions from my own experience.
You don't need as much as you think. I know that 10 grams of mica might not seem like a lot, but consider that you could easily make 20 eye shadows (or more) and at least five nail polishes out of that amount. Wow! That's a lot of mica!
Try to break down how much you'll use in a product. Take an oil, for example. If you're making a 100 gram batch of lotion, you are unlikely to use more than 25 grams of one oil. A 125 ml or 4 ounce bottle will help you make about 5 lotions of that type. Odds are, though, you're using less of one oil in a lotion - let's say 15 grams - which means a smallish bottle of oil will help you make 8 bottles of lotion!
When it comes to oils, my suggestion is to get the 4 ounce or 125 ml container for things that don't cost too much and see if you like the oil. I encourage you to check out these posts on learning about the skin feel of your oils and butters, which is a great way to save money on supplies! You really don't need to have every single oil in the store - yeah, I know, that's rich coming from me, eh? - and you don't need every exotic oil in the place either. You can get away with four or five really lovely oils that you spend your money on instead of having an entire library!
Take a look at the products you make regularly and do the math on them to see which ingredients you use a lot, and which ones you use a little. Take something like polyquat 7. I use it at around 3% in my body wash and shampoo and, occasionally, in a lotion. I tend to make 1 kg or 1000 grams of body wash at a time, which lasts my family 4 or 5 months. So I'm using 30 grams of polyquat 7 x 3 times a year = 90 grams of polyquat 7 in my body washes. If I buy a 120 gram (4 ounce) container of polyquat 7, I'm set for the year for body wash! (I do use it in shampoo, conditioner, and leave in conditioners, as well as lotions, but I wanted to make the example easy!)
Some things like Polawax or Incroquat BTMS-50 are ingredients that I use in a lot of products, so I'll buy in the 227 g (1/2 pound) to 454 g (1 pound) amounts. I'll buy butters at higher amounts - like 1 pound or even 2 pounds - when I'm making lots of anhydrous things because I use butters as the base for things like lotion bars and whipped butters.
Really think about buying the larger sizes. Although it might look like a great deal, if you're throwing half of it away, it's not. Think about the expiry dates of your products. Something like liquid Germall Plus will have a very long life span - over two years - so buying a slightly bigger size makes sense. Something like hempseed oil has a very short life span, so buying more than you need might mean hucking out half of it at the end of three months.
As a side note to this, whenever you get a new ingredient, put the date on it. It'll give you an idea of how long you can keep it.
I know it might seem like a pain in the bum to order smaller amounts, but you can always order from the supplier again. Yeah, I know, putting in an order might take time and waiting for it to arrive sucks, but if you order again in a month, they might have some new stuff you can play with in the store! (No, wait, that's a bad suggestion if we're trying to save money!)
As an aside, that picture is of the "6 ounces or larger" bin in my house. I have a shelving unit that is organized into 1 ounce or smaller, 2 ounces, 4 ounces, and make-up containers sections because I have too many of each thing. I really do like packaging!
Heating, holding, freezing, and thawing your oils and butters