My suggestion for someone at the intermediate level is don't look for a progressive structure that continually builds upon itself :-D

I hear a lot about the "intermediate blues"--people who get stuck in intermediate language hell and feel like they'll never get out of it. I'm at the intermediate level, but still feel like I'm improving. This is because I have a lot of contact with the language throughout the day. I don't study progressively or systematically. I just use the language a lot.

Some examples:

-Using QQ, 微博 and 微信 daily

-Reading books and internet articles in Chinese

-Listening to Popup Chinese podcasts

-All my computing devices (PC, cellphone) and websites I regularly use (Facebook, Google sites) are in Chinese

-I live in China and:

*My wife and her family are Chinese

*All my coworkers are Chinese

*Many of my friends here are Chinese

*Most casual conversations I have here (in restaurants, taxicabs, etc.) are in Chinese

-I also make flashcards out of stuff I see in real life. Not long HSK word lists, but, say, something my mother-in-law says, or a sign I read on the street.

My advice is to increase your contact with the language, and learn things as you go. At your level the heavy lifting--learning the basics of Chinese characters and tones--is all out of the way. What's left is the slow accumulation of vocabulary (chengyu, rare characters, slang), some finer points of grammar (which Popup in great for), and then one day, if you're ballsy, 文言文.

The other day I learned the word 羊水 (literally "lamb water"), which means amniotic fluid. I just love that two of the first characters I learned, put together, make up a word so rare I've never used it.