I’m thinking of changing my name from Ali to something more masculine, since Ali is just the start of my birth name, BUT everyone at college knows me as Ali and it’d be easier for them to keep using the name Ali
What about Al ? There are a few first name sites, you might look up your birth name... often further short forms are given... some have another first name... Some think about using the male name their parents thought of... Some use a name that inspires them, or they read about or see a few times... Some go through a process, using i.e. a unisex name and later a name they like...
Ali can be a masculine name, since it can be used as a nickname for Alistair. Though it is generally not seen as a masculine name, it might be helpful just for you to see it as a more masculine name. If you'd rather change it, a name that's similar to Ali would probably be easier for your friends to remember. Ultimately, you should just do what you want because it doesn't really matter if it would be a bit easier for people to keep using the name Ali. If you're fine with it, then by all means, just keep going by Ali because it's the easier option. If it makes you uncomfortable, then don't worry about other people, choose a name that feels more comfortable for you, and just be patient and give them some time to adjust.