For anyone beginning any instrument, your progress will be much faster and more certain if you get yourself a good teacher.
That teacher > pupil thing has been going on for thousands of years in just about every field of human endeavour so there must be some advantage, no?
Though I admit there’s something to be said for the DIY mode, the interesting detours, the serendipitous discoveries, the two steps forward one step back.
Of course nowadays with YouTube and Skype and online tutorials there’s a powerful middle ground, neither with a teacher in the old sense (sitting in his parlour for an hour, do it this way, not that way) nor entirely on one’s own.
About the reading of sheet music, that all depends on what your goals are, what sort of music, what sort of playing environment, and also your personal learning modality.
For Irish traditional music most players didn’t read music in the old days and probably the majority don’t read music now. One often hears the opinion in ITM circles that learning to read music will damage one’s chances of becoming a good traditional style player. While I don’t understand how that could be, it is true that to learn ITM it’s better to set sheet music aside and learn the tunes by ear from good trad players, because developing a good “ear” is crucial (whether or not you also have the ability to sightread).
When I have students I leave it up to them. Some prefer to learn by ear, some prefer to be handed sheet music. I don’t think it does any harm to address both modalities, but if someone is too tied to the sheet music I have them put it away and work on their “ear”.
If your goals are outwith ITM it’s a different matter altogether. There are many people who play whistle in Church settings and in some of these settings the music is learnt by ear, while in others printed sheet music is followed. If one’s musical environment requires sightreading then sightread you must.
I find sightreading very handy at times, for example if I have to play a certain tune at a gig, a tune which I don’t want to take the time to memorise, and one which I have no desire to ever play again. I’ll scratch it out on some paper, play the gig, then put the music in my filing cabinet, in all likelihood never to be seen again.
Good luck! It’s a fascinating lifetime adventure to be sure.