Hi,
I self taught myself Economics, Maths and Politics in 2016, sat the exams in May 2016, came out with ACC in the order above.
I would say the self-teaching isnt the issue, the biggest issue for me personally was procastination: no teachers bugging you, no peer pressure, you tend to lose the competitive buzz you'd have amonst your peers. so dicipline, for me was key.
in terms of content, they were all quite mediocore. i mean, economics just made logical sense to me so i understood. maths i had a natural talent for at gcse (got an a*) obviously i failed one of my maths modules which bought my grade down to a C.
Politics too, wasnt too hard for AS. I shouldve have and probably could have got a low A or high B if it wasnt for extenuating circumstances 1 week before my exam.
Also, 1 key thing you may need is exam expertise, youtube clips, revision guides, all pdf files from here n there just cannot replicate your teachers expertise in terms of answering essay based questions. id recommend a tutor who knows thier stuff for maybe 6-10 hours pre exams.
other than that, AS wasnt too hard, now that im starting A2 - im dying
all the best