If you aspire to be a good or even great singer, you have to know what the standards are. I am alarmed that many young singers these days don't seek out recordings of the great singers. They tend to look on Youtube for anyone singing the piece that they are learning as an aid for memorizing, and don't exercise much in the way of critical judgement as to what they hear.
It's not difficult to find lists of all the greatest singers online - Wikipedia is a very good resource for this. Print out the list and then hunt on Youtube for these singers so you can hear for yourself how different the greats interpret a song or aria, and how they manage technical issues. It's especially useful to see video of them singing live if possible, as that shows a lot of the physical process that they go through to produce their sound.
Another great free resource is your library. Many libraries have good collections of CDs you can borrow and study at home. When I was a student at the Sydney Conservatorium in the 80s I spent hours in the Con Library listening to records of singers I was interested in, and then I would try to emulate the things I admired about their tone, control, use of dynamics, expression, language pronunciation and so forth. It's fun and is a very worthwhile way to educate yourself about your chosen profession.