Syringes are what you'll be using to store and push in the oil. As demonstrated in the diagram, the barrel is what you'll pull the oil into. The plunger is what you'll press on to inject at the injection site.

For syringes, you should buy a 1ml syringe. Make sure to not buy any "oral syringes."

You can buy either the Luer Lock or Luer Slip syringes, these are the 2 types of syringes you can buy. As referenced in their names, the Luer Lock syringes locks the needle more in place. So it's harder to remove the needle after being attached, making it more secure. Meanwhile, the Luer Slip syringes allows you to attach and deattach the needle, allowing you to remove the needle after you've attached it. That's the only difference between these two categories, depends merely on preference.

Either way, I made a list of sources you can buy Syringes from so you don't mess up. Links from Amazon are included, so this purchase should be easier compared to buying bitcoin. Listed brands as well. Don't worry about brands, they're all good quality, I just listed them because it's informative.

Here we have Injection Needles, this is what you'll be using to actually draw up the oil and inject it. You'll slip the needle onto the syringe's tip to then proceed into injecting. I'll be listing two types of needles, intramuscular needles and subcutaneous needles. The differences being in two things, the diameter (gauge) and length (inches) of the needles.

Intramuscular needles are meant to inject in the muscle, thus the intramuscular section of the word. Since we need to inject into the muscle, the needles used are longer compared to subcutaneous needles. Subcutaneous needles, subq needles for short, are used to inject right beneath the skin. This layer of the skin is called the subcutis or the hypodermis, containing a lot of fatty tissue.

So you may be wondering, why would I use intramuscular needles? Simply because it's been shown to be more effective and the preferred method of injection for decades. Although subq needles still reach the therapeutic ranges required for HRT to be effective, in estrogen and testosterone. So this is mostly up to personal preference and if you think 1 inch needles are too long, try buying subcutaneous needles instead.
I made a list of sources you can buy from below. Listed brands as well. Don't worry about brands, they're all good quality, I just listed them because it's informative.

For the sake of convenience, a lot of manufactures make kits where syringes and needles are sold together. A lot of times, these kits are actually cheaper versus buying the two separately. There are no downsides to this, just an alternative for those who want to buy kits instead.

I made a list of sources you can buy from below, listed brands as well. Don't worry about brands, they're all good quality, I just listed them because it's informative.

Alcohol Pads are what you'll be using to sanitize the area you'll be injecting at. You rub the pad on the injection site, typically your thigh, then you inject at that area.

The pads typically come in packs, in large bundles. So don't worry about running out of these soon. I made a list of sources you can buy from below. Listed brands as well.

Buying band-aids are optional, but I still included them because bleeding may occur and it's useful to have these around just in case. To avoid bleeding though, simply apply pressure for 10 seconds onto the spot where you injected after completing your injection. You can do the same trick to avoid oil leaking.

I made a list of sources you can buy from below.

Sharps Containers are where you can store used needles and syringes after you're done injecting. These are also called bio-hazard bins and specially created in safely deposing biohazardous waste. If you don't want to buy a sharps container, you can utilize a simple plastic tupperware container or other alternatives here to store the waste.

To depose of sharp containers, you can throw it away in your household trashcan or garbage bin. Please do not recycle, just throw it away in the regular trash.

Even then, I still made a list of sources you can buy sharps containers from.