Ego battery, good pen style and most common get started unit, rugged, dependable, tried and tested so no fault there. The CE4 clearomizer, again a decent new vaper atomizing attachment as it comes with an atomizer in it, and is a tank, so holds a bit more liquid than basic cartomizers, and you can tell when it is time to refill. Basic expenses at this stage to look at, are try some different liquids, even different brands, sampler packs a decently priced and a good place to start. 2 PAD 24mg sounds about right to get started, maybe try some 18mg, see how that works if you are chain vaping and getting nic overdose (nausea, headaches, can't sleep real well), also try different PG/VG blends, the biggest part is finding liquids that keep you satisfied, and yes nicotine content affects throat hit.
PG - Thinner, transports flavor better, stronger throat hit
VG - Thicker, gives some liquids a sweeter taste, produces better vapor, less of a throat hit
Next expense, a couple more batteries, preferably Ego-C Twists in as high a milli-amp hour rating as possible. The Ego Twist is variable volt, you can dial up or done the voltage output to increase flavor, vapor, and throat hit to your liking, basically turn it up in 0.1 volt increments to the point the liquids starts to taste harsh or burnt, to harsh back down 0.2 volts, there is your max setting, burnt 0.3-0.5 volts. Higher milli-amp hours (mah) on the batteries, the longer they last between recharges, 900 to 1000 mah suggested.
Some more tanks, and spare heads for those tanks. Later you can experiment as your funds allow it, probably look at iClear16 and iClear30 attachments as uprgrades, which offer replaceable coil heads and wicks, the iClear30 is a 3.0 milli-liter tank over the CE4 and iClear16 being 1.5-1.6ish mills.
Dripping atomizer with a drip tip, the basic 510 dripper is durable and rugged, makes great for sampling juices before commiting them to a tank, and works as a great backup if a tank fails. These produce the greatest flavor, easy to clear out and clean, and last a long time, downside they can only accept 3-5 drops of liquid at a time.
Cartomizers are a cousin to the dripper atomizers. A coil with a little wick in it, surrounded by a polyfill material to hold juice and transport it to the atty, a little taller, and can hold upwards to about 25 drops of liquid first fill standard length to 35 drops first fill for the taller one. Flavor is muted a bit, but they are portable, basic, easy to maintain, and last about a week of heavy use, plus they can be notched or punched on the side and put into a DCT or Carto Tank, or can be purchased pre-punched specifically for that reason.
**************Biggest Advice******************
Water, drink lots and lots of water. Vaping dehydrates you so keep drinkable liquids close at hand at all times