Your timeline will show recent posts by other people you follow.  If you only follow a few people, you will likely have periods of time with no new posts on your timeline.  The best way to remedy this is to simply find more people to follow.  There are a number of ways to do this.  One is to make use of people you already follow.  For example, if someone you follow reposts something by someone else, if you also find that repost interesting then that might be someone worth following.  Also, read the comments of others on the posts of people you follow for more candidates to follow. 

 ... also, most clients have other ways to find posts - like searching hashtags (though, i don't do much of this myself, tbh).  #asknostr seems to be a popular one.