True!
To be fair, all the tutors I met were prepared, nice and enthusiastic - so nothing to complain in this sense. But traditional, long courses are just not for me. 
I didn’t do a structured course, so I don’t know exactly what kind of practice you’ve been doing besides the challenges - which can make quite difference in how easy or hard, and how boring or interesting you might find “classic” lessons, I believe.
I’ve only participated to random lessons and groups of all levels and the main difference to me seemed that in Sylfaen tutors speak unnaturally slowly (and use English more often to explain rules or translate), most exercises are pre-structured -like specific questions, repetitions, pre-taught vocabulary, reading, etc.,
In Canolradd +, teachers speak more fluently, practice trickier grammar and there’s more chatting involved (what us SSiWers are usually better at, compared to traditional students!)
I did Level 1 and 2 in one summer, and a few months later went to Wales for a week straight to all-levels chat groups or spending time with people speaking at normal speed to me all the time, and I survived! 
So for classes I would agree it pays to be ambitious and try a more advanced course - especially if it’s a short one like one-day, weekend or week.
Books:
I started reading way later, and I was happy to start from Mynediad books because I could follow and enjoy the story without needing a dictionary - i don’t have the patience to stop and search for words all the time!
Also I’ve recently read about how reading easy books may help consolidate structures and vocabulary in a more efficient way rather than keeping on thinking in own first language and translating word by word in your head every time so I think it may be worth starting lower and going up, instead.
But in any case, it’s all a bit subjective, so this is just my opinion, and I’m sure you’ll be fine whatever you go for - in worse case, you can always chance as Sue said!