Unfortunately things in life aren't fair. Webcomics have a large degree of luck involved. If the right person with even a small amount of influence notices your series and spreads the word it can cascade into much more.
Features aren't really what they are hyped up to be. We worked like crazy for a year trying to get a feature and never did. Finally a summer intern picked one of our series for a Spotlight. We though it would be a game changer... it really wasn't. Three days on the homepage doesn't do as much as you would expect, considering that most desktop readers only visit a few times a month.
Yes, the Spotlight gave us a bunch of subs and views for a short period of time but many of them unsubscribed in the weeks that followed.
Don't beat yourself up over not getting a feature. It's not worth the mental anguish.
We have the 3/10ths rule. You'll only get about 3/10ths back in return for what you put out. For example, we quarterbacked a review about Tapas in a digital magazine. The article featured nine webcomics on Tapas. You'd think creators would be super thankful... we got three thank yous private messaged and one of the three did a fan art as a special thanks. That's all... for something that took 15-20 hours to make happen.
You can like/comment/promote other creators work, but always keep in mind that it's a gift. Don't expect anything in return. Otherwise you will end up seriously hurt and very disappointed.
Having spent thousands on ads we can tell you that most ads do not do anything. Your best performing ads are Google Adwords, Project Wonderful, and TopWebComics $1 Daily Sponsorship.