For all you Instagrammer's, you may have noticed pictures don't just pop up in chronological order anymore. You can kiss that goodbye. It is now focused on engagements. Instagram is now generating your news feed to your interests, making it more personalized and generic as ever. Your pictures will no longer just show up on someone's feed unless that person is active with your posts (likes, saving, commenting, looks at your profile). Your likes have probably gone down.
This is a win-win development. If you get a lot of engagements, it will be shown to more people. If your post fails, the audience is a smaller percentage. You either thrive, or you sink. You literally need to put time into your posts. If not, only a few of your followers will even see your posts. In my defense, this defeats the whole purpose. I follow people because I want to keep up with their posts. The whole point of social media is picking who you follow and picking what you want to see, not Instagram telling you what you want to see.
So Instagram is not just used for marketing matters. Although Instagram posses great use for marketing, it is not its main use. I use this for documenting my life. Stop treating this as if I am selling an As Seen on TV product. Social media is now a competitive market. In order to get engagements, you must use marketing, advertising, and design. Not only does the time of posting matter, because the first hour and how many likes you get is crucial, but now your page needs to be pleasing to the eyes. Professional photos, promotions, contests, giveaways, tagging the right people, using the right hashtags.
My advice is using apps to tell you the best time to post, such as Buffer. This will set reminders to post at the best time and give you content feedback. Or, Preview. This will show you your picture on your feed before it posts, so you can see if it matches your theme. It also comes with presets, and analytics to track your engagements and the best time to post.
Make your posts look interesting and edit them. VSCO has great presets that will make your pictures stand out. If you are serious about Instagram, you need to invest more time into your posts. Strategize and use resources before posting. You can join groups that will like pictures to help keep your posts showing up on others pages.