Hello!
I’m a new transfer student at University of Maryland.
my major is mathematics, and I’m gonna major in philosophy as my minor.
I know Oxford is the top school in the world, so my chance is really small.
Since I transfer from community college, my GPA will be reset.
Please let me know how to be a solid graduate candidate in math.
Just like any other graduate program, you need to get a significant amount of research experience and develop relationships with faculty who know you well enough to provide very strong letters of reference.
The most important thing to realize about grad school in the UK is that it is much easier (in relative terms, you still need to be a very strong candidate) to get admitted than to get funding. Funding for overseas PhD students comes from a limited number of scholarships, often from their home countries, because you are just doing research, not working as a TA. As a result a PhD is also completed much quicker (3-4 years).
So the first question to answer is whether you could/would self-fund? That’s generally a bad idea when most reputable US PhD programs do offer funding as part of the package.
If you want to get funded then the most obvious (but not the easiest) way is to win a Rhodes scholarship. Do you believe you would be able to compete at that level?
If going to the UK for grad school is an ambition then you should also look at Churchill scholarships, which are often used to take Cambridge Part III maths. That is the typical level of preparation assumed for an Oxbridge math PhD and doing well there (competing against the best mathematicians in the world) would stand you in good stead for any prestigious math PhD program. Profiles of winners are easy to find.