If you know that you like all the juice you have or will be getting, you don't need an atomizer or drip tip.
I guess you could test juice in a Vision Clearo, but its kind of a rough way to do it.
If all you use are Clearos, you don't need any cone. You really don't need that anyway, but it's nice for attys, dripping or cartos.
You can get by on that list. Are you really saving any money though? It seems like shipping would make up the difference, unless you get it all at the same place. But most vendors price their kits to be cheaper than the individual items.
When I've tried to do it that way, it turned out that atty or the pack of cartos I didn't need was going to cost me $2.