If you select the Blood Arcanist option, it replaces the Exploit selection you get at 1st, 3rd, 9th, and 15th level. Do you have to wait to select the Extra Arcanist Exploit feat until you hit 5th level and 'officially' can choose your first exploit? or can you spend you feats to get extra exploits from the get-go?
http://www.d20pfsrd.com/classes/hybrid-classes/arcanist
http://www.d20pfsrd.com/classes/hybrid-classes/arcanist/archetypes/paizo--- arcanist-archetypes/blood-arcanist
As I understand it you do not have the feature until level 5...
yes, wait till 5.
If you haven't received the ability from your class you can't take extra. See the extra hex feat and witches FAQ that says this.
