Your request is pretty broad but here’s what I think you could start with. If you understand SEO Google Ad Words is a good place to start. Not sure what platforms you’re looking to advertise on but the built in Facebook business console is free and great for running multiple ads for multiple accounts on FB and IG. For hashtags I haven’t found anything better than good old fashioned human research. There are apps that will find more hashtags based on a key word but they usually return very broad hashtags when you’ll probably want more niche hashtags, especially now that only top posts are shown in hashtag searches on IG. Insights can easily be found on any business account for free. What exactly are you looking for in influencer marketing? A way to be connected with influencers or a way to manage influencer campaigns?