My plan, reasoning below.
[X] Plan: Spells, Attributes, and Classes
-[X] Case III: The Riddle of Riddle - Digging through the archives for so long has given you a good grasp as to who walked these floors in the last two hundred years. There were mentions of someone, you still remembered. There had been some records history of one of the greatest minds that walked this castle, maybe not as special as Sally-Anne or even Dumbledore, but still … Who was he? (2 Actions)
-[X] Write a Letter (Free Action) – To your parents. Talk about the amazing things you have discovered at Hogwarts. The book which they have sent you. Tell them about your experience with the Dementor but reassure them that you are fine and made it out whole, if a bit shaken.
-[X] Quidditch Round 2, Hufflepuff vs Slytherin – It's time for the second game of the year and while you have a lot of things that you'd like to focus on, most of the school will be present here. Go and watch the Quidditch Game. It could be interesting and if it is not, well you will be high enough up to watch the clouds instead.
-[X] Twenty Thousand Leagues Under the Sea I (Takes 3 Actions, can't be taken in the same month as Break through your Horizon and What hides behind trees.)
-[X] Stage II, Dreams of old (Takes 2 Actions)
-[X] Train, Learn, Achieve – Creativity
-[X] Train, Learn, Achieve – DADA
-[X] Train, Learn, Achieve – Charms
-[X] Do your research –Avifors (Needed for exams at the end of the year) – Transfiguration.
-[X] Do your research –Cheering Charm (Needed for exams at the end of the year) - Charm.
-[X] Do your research –Protego (Basic Understanding) – DADA.
Reasoning: Took the Case because those usually have some payoff. They either give us experience or drive the plot forward in some way. Letter to parents because we haven't talked to them and it is a free action, they probably miss us. Quidditch because Jacob needs social exposure. It isn't healthy for him to spend all his time alone. Hopefully he can form some bonds with his yearmates. I wanted to do the Horizon Mountain exploration but chose the Lake instead because I believe the mountains will be more dangerous. At least the Lake is close to the school so if we get in trouble we are close to the hospital. Probably better to save the Mountain Secret Passage for later on in the year when we have more spells under our belt. Dreams of Old because we got some good stuff last time we did them. Also, our parents want us to know more about our heritage, we should oblige them.
As for the Personal Actions. Did Creativity because it is one of the main skills that effect magic (I went a bit light on Attribute training this time, I know. Next month we can do a few more actions). DADA and Charms to get them to P-. Two essential Charms that have a low DC and to get them out of the way. Protego for the Dueling Club and because we have been in a lot of dangerous situations so far and it seems like a good idea to get some defensive magic.
Edit: Regarding the Random Encounter. I ended up changing that to Quidditch . I put it in because I think it is important for Jacob to have some social actions every month. It isn't good to spend all of one's time cooped up studying.