I like Shadow and Flame because I love the idea of escaping from the Balrog of Morgoth and beacause it's well balanced, you can quest without too much effort, fight a lot (you need quite a lot of that but since tactics is my favourite sphere I love it), and you get to use secrecy cards (which I normally don't use, especially cards like timely aid) because the first quest card resets your threat to 0.
As for The Redhorn Gate it is one of the more varied. Grand Spleen explained it quite well so I'm just gonna say that, maybe, without all of the mirkwood cycle APs, and only 1 Core Set it might be tough, but it's not true that it's way more difficult solo (I played all of the scenarios multiple times both solo and in 2 player games with my girlfriend). The only scenarios that are actually tougher the more player participate are : Road to Rivendell (not very hard anyway), The Long Dark (that you shouldn't miss because there's the mighty Hama of Rohan, also not very hard), Shadow and Flame and the Massing at Osgiliath (this one is much harder in multiplayer while it can be a piece of cake solo with a low threat deck).
In conclusion, my advise to you would be to buy the APs in order both because of how hard they are the farther you go (for instance at a certain point you really need hands upon the bow if you plan on using Legolas at his best), and because of the story that is told. But if you prefere to get them without a particular order I think you should also see which cards come out in what AP. Keeping in mind that most people's favourite scenarios are The Redhorn Gate and Foundations of Stone.
Ah I was forgetting to say a few words about the Hills of Emyn Muil. In my opinion it's quite cool. After a lot of fighting and cancelling shadows and avoiding threacheries you must focus on exploring locations and travel through this scenario with cards that sometimes are useful only in this one (like ride to ruin, strenght of will and the likes). I like it, maybe it won't hit my top five but it surely is one of my favourite 2 or 3 from the mirkwood cycle (the one I dislike the most being Return to Mirkwood because it's thought for multiplayer only, pretty much like Dol Guldur, so to beat it consistently in solo play you must build an almost perfect deck and most importantly you must have quite a good amount of luck).
Also keep in mind that reprints from the mirkwood cycle are about to come out, so if you want to get the The Hunt For Gollum you should be able to in a few weeks.
My last advise is to get the stuff from sites like amazon or the book depository (even better and with free delivery worldwide), especially the bookdepository is the reason why my girlfriend and I get to buy all the packets and expansions from AGOT, LOTR and SW (because of the good availability and very good discount). I don't think we could have gotten three core stes without these sites because the retailer price is like 12 dollars higher. Moreover being stuck in Italy we wouldn't be able to find the stuff (and most importantly not in english)…
Hope I helped you out !