Instagram ads can easily be done at the same time as FB ads in Facebook Ad Manager - and FB can do the hard work of optimizing them. If you are new to Ads I’d recommend that. There are plenty of free tutorials on how to place Facebook ads, so google them before you start.
In regards to building a marketing strategy, there is no simple answer. But I would start by identifying your audience and then trying to reach them on places online that they hang out or populate.