If you believe you have what it takes to be an effective reviewer/influencer, then you'll have to prove that to manufacturers and retailers by showing them. This entails spending your own money on the gear you want to review in order to establish yourself as "worthy" of getting free stuff for review.
Anyone can ask for free stuff. Only a small percentage can/will actually make a review on them. Of that small percentage, only a few can actually establish themselves as an effective product influencer or reviewer.
Prove it and the free stuff will follow.