A tracker mortgage is very similar to a variable rate mortgage with the difference being that the interest rates follow those set by the Bank of England, rather than by the lender itself. As with a variable rate mortgage, a tracker mortgage has the same pros and cons, with potential savings as well as the possibility of increased repayments.
Which one you decide to go for depends on your personal circumstances and financial situation. The safest bet is a fixed rate mortgage, since keeping an eye on interest rates for first time buyers takes time and effort, and you have better things to think about! Though feel free to discuss your options with a mortgage advisor as, depending on your situation, other types might work better for you.