Please list masechtas that easier to learn.
Don't mention Megillah I already learned that one
Let's restate the question:
I just finished Megillah, and am now looking for a complete mesechta that's comparably easy-to-learn-and-finish.
So let's consult this table:
Two easy measures of a mesechta are its apparent length, as measured by daf; and "density" -- how little commentary does each page have. (The less commentary, presumably, the easier the material as it needs less explanation.) Additionally, tractates in the same Seder tend to cover related material.
Megillah ranks #9 on shortness-by-daf, and #4 on ease-as-measured-by-density, and it's in Seder Moed. By that logic, Taanis is probably your best bet: it's also in Seder Moed, #8 on shortness-by-daf, and #6 on ease-by-density.
(Let's look at the top five ease-by-density: Brachos is double the length; Krisos assumes a whole lot of background knowledge so that our poor protagonist can violate fifteen impossible things before breakfast; Horiyos is kind of abstract; you did Megillah; and Sanhedrin's super-long. Then comes Taanis!)
The very first one. You Berachot, the first page. It has been tought and explained extensively and you can find many resources related to it. Search Daf Yomi and you'll find it.
I think you should learn Brachos and Perek Eilu Metzios from Bava Metzia. They are relatively easy to learn and there are tons of resources online to help people studying them.