Noob - expansions

[Lokisama]

There will most likely be a Heavensward+Stormblood combo when stormblood comes out if you want to wait for that long but as the people mentioned above all the content that comes in heavensward is locked until you get the expansion.

[Niwashi]

There will most likely be a Heavensward+Stormblood combo when stormblood comes out

There's no non-combo version, actually. All copies of Stormblood include Heavensward. Paying for HW separately is only for getting access to it prior to Stormblood's release.