OP, the short answer to your question is, do well in calculus 1 and the gre quant section, that's something you can definitely do in one year to strengthen your application.
The long answer...
1. Saying trig is not useful for polisi phd is wrong. Yes you won't write your dissertation on that, but you need basic stuff like that all the time for college level math, as well as polisci method courses if you enter a phd program with serious training.
2. Calculus 1 is more useful for you than linear algebra at this moment. Also don't waste your time on stats courses now. You need the full calculus sequence and one linear algebra to take probability theory, after that you will be in a good position to learn stats.
3. People who got into top programs typically have very high gre quant scores, but most of them don't have much math background. So relax, focus on what you can do now.
4. Be cautious about information you get from gradcafe and PSR, where people who think anything with number and greek letter is "math" intimidate you with stuff they don't really understand.