He got 3 episodes last season with both Gauntlet of Fire and The Times are Changeling important for world building and Spike's character develpment and the later very plot relevant as well. Dungeons and Discords was a Discord episode so a big deal and the first guys only episode and Spike even got big role in the Chrystalling premiere.
Not every season needs to be season 6 for him. In season 5 he had only Princess Spike which was displeasing to many and inconcequential episode and he was Twlilight's sidekick in the finale. That was similar to season 1 where he has only one episode in the end of the season so last season was unusual as was season 4 with 3 episodes as well. Usually it's two.
Imo now that the show promotes more supporting characters 1 episode is a good number for Spike if he has nice supporting appearances like he had in the first 3 episodes. I am sure he will have a episode at one point and he could even still have two. Or he could have two next season.
Imo I think he should have episode visiting Thorax and the Changelins so that relationship can be built on and it's an interesting episode where we can learn more about the changelings. Spike has had so many episodes when you look at the entire series that what should matter is that they are good ones which character develoment, nice supporting characters and plot relevance. Quality over quantity. Otherwise it's too easy for the writers to write a usual Spike episode where he messes things up. I hope they keep pairing him with interesting characters like in season 6 with Starlight, Ember, Thorax and Discord where he can shine. Too much spotlight for him is not beneficial.