I use it a little for my shop account - I have a personal account in addition to my shop account, and tend to stay logged in to my personal account more. Using hashtags when posting photos helps to get others to see your photos if you don't have a lot of followers, and you can link your twitter/facebook page to instagram so that when you post a photo it automatically posts an update to twitter/fb.
There are probably a few "hacks" to be able to post to instagram from your computer - a simple google search says there are sites/workarounds to do that - but an easy way to use your good photos through the phone app would be to store your photos online, like google drive/photos or box. If you have those apps installed on your phone, you can access the photos that way, and just crop them into instagram's square format.
Using Google drive/photos or box doesn't take up extra space on your phone's memory either, and you can use those apps to periodically transfer/backup your phone photos and access them on your computer later on.