Any advice I offer is only from my own experience, as I have not had formal lessons, but I have picked up quite a lot of diverse knowledge on various aspects of music, though less on Classical than other genres.
As a teenager I tried to play trumpet, from a tutor book, and I also did piano 'by ear', but refused to have lessons when my mother wanted me to. My younger sister and brother had piano and violin lessons, and got several grades.
Aged 21 I had drum lessons from a professional teacher for 3 or 4 years, but never became as good as I had hoped. However, I did play for forty years in pubs, clubs, pantomimes and stage shows, and with old time music hall, and a versatile barn dance band. Working as a Teaching Assistant I taught recorder clubs for ten years, had a Year 6 keyboard club, and coached children on percussion to accompany the Christmas production each year.
In my 40s, I started learning electronic organ, two manuals and pedals, from Kenneth Baker books, which was great fun! So, although none of my experience is 'formal' I have helped children and some adults learn a certain amount of music. I always maintain it should be 'fun', and not TOO much like hard work.
OK: so you know where middle C is, so you can also find all the other Cs. But do you know why the BLACK notes are grouped in 2s and 3s? And why there is NO black note between B - C nor between E - F ? Discovering that, and starting to understand it, is the basis to theory, harmony, scales etc. It is also why Western music sounds different from Oriental, Indian and Arabian music.
When I was learning organ, I could read Treble Clef, but not Bass Clef, and I did the accompaniment from Chord Symbols. Eventually I realised that Treble and Bass are NOT two different things (which at first they seem to be) but are both part of the GRAND STAFF. I'll give you a link to that, which you can read at your leisure. I won't be around for the next week, but I'll check back in due course, and see if any of this has made sense to you!
www.essential-music-theory.com/grand-staff.html