First of all - WARNING:
DO NOT use passive built-in droppers (first option on the photo). While this setup might be acceptable for some applications (such as dispensing oils into a burner or mixing fragrance into a massage oil base) this is entirely unacceptable for perfume making because speed of dispensing drops is highly unstable.Built-in (screw on) glass pipettes or disposable plastic ones produce much better (stable) results.
You can find different pipettes, but so far I prefer small ones available from Creating Perfume (price: $5 for 50 pipettes).
Sometimes, when you are doing a lot of mixing you can also use standard plastic straws. The ones sold in Ikea are rather thin and semi-tranparent ($1.99 for 200) making them an excellent option for dispensing oils.
Here is a short video explaining how you can use straws to dispense oils:
Have fun with you creations!