I use the Ikenvape i06 atty (requires i06 drip tip). Just 3 drops in the drip tip and it's good for about 5 draws. The taste will start to change and you drip 3 more drops. Ikenvape has tight quality control and the attys last a long time.
You should match the resistance to the battery voltage unless you have VV.
1.8 for 3.4 eGos and 2.5 for 4.2 (3.7) eGos, 3.5 for higher voltages or cooler (low watts)
vaping.
Enjoy!