My answer to you is never stop buying things. Never. Every paycheck buy more clearos, cartos, atomizers, tanks, batteries if you can, mods, and juice. If you go by that ethic, you'll know when you can stop buying clearos and tanks and cartos and atomizers and juice. You'll figure out which juices you like best and you'll buy 30ml bottles of them and you'll never be unsatisfied. You'll just be replenishing what you run out of at that point. Until your there, keep buying. Buy mods, buy extra batteries to put in the mods, buy what you can afford and don't look back until you are completely confident in the things you have. I don't mean splurge and go crazy, and by no means do you NEED 5 mods or 4 eGos but if you want to be completely care free and if you want to have a tank of A. juice filled and a tank of B. juice and a clearomizer of C. juice each on their own device so you can just pick one up and vape, keep buying. Keep buying. What you NEED you already pretty much have.
2 minimum, but 3 or 4 eGo batteries is best if your ONLY going to use eGos. Otherwise start looking at mods.
You might want a few atomizers for when you just want to drip or you just want a small taste of a juice.
You might want to try a rebuildable atomizer or two because it'll last forever if you learn to rebuild it.
You might also like to try a rebuildable tank system such as the smoktech R tank or an Aga tank.
You might want to have 2 or more 5 packs of 45mm cartomizers on hand for your cartomizer tanks.
You might want to have a lot of either carto tanks, or clearomizers, or vivi tanks for holding many juices.
You might want to start trying out a lot of juices. When it comes to buying juices @ first:
Go for sample size first and then buy bigger when you know u like it.
You might want to start buying mods, start looking at mods in the "Post Pictures of your PV" thread on ecf.
You might want to get a wide variety of drip tips for color coding your juices or remember which is in ur tanks.
You might want to try different types of clearomizers, T3 bottom feeder or the visions or redux or vivi mini.
You could start thinking about DIY juice making and buy a kit that includes everything you need.
You might want to stock up on stainless mesh or wick material if you plan to rebuild things.
You might want to start thinking about what type of mods you'd like to eventually own.
Mechanical mods, telescoping, variable voltage, variable wattage, kicked or unkicked with low resistance heads?O
OR you can stop where your at. Just stop. Just stop and vape and be healthy and happy.
Its all up to you. But what you need, you essentially have.
You need 2-3 or 4 eGos or Mods, some clearomizers, charger, and some juice.