Here are the meanings in this context: Reach (noun) = Your potential influence on the world, or on your market. Having a big reach means many people can connect with you. Having a small reach means you cannot connect with too many people, you have a smaller influence in the world / your market." micro-influencers = Influencers that have a smaller influence (a smaller reach). To put you off = To make you not want to do something. To make you change your mind about doing something. So, this sentence means, do not let the smaller influence of micro-influencers, make you not want to do this. Don't be discouraged/disappointed in micro-influencers' small reach, there must be some other advantages to them.

Oh thank you for your reply. it really helped me :)

For what I can understand, "reach" could be a smaller amount of this group of micro-influencers and "to put you off" would be something along the lines of "make you change your mind in doing something" "create instability" "make you less interested in something". I hope I have helped you.