When you say Topcoder, I imagine the first international competition I participated in as it had a huge impact on my life and changed it a lot. The first year was the most challenging thing I had ever experienced. I loved to wake up at 3 am and spent several long weeks participating in Marathon Matches. Nowadays there are many more competitions, some of them are slightly different, some of them even do better in some sense, but TopCoder still stays in my heart and I can't imagine myself to ever stop competing in its competitions.
It is by far a silver medal from this year ACM ICPC (2015 Morocco).
I love to do all kind of sports, team or individual. I also enjoy to watch sport. Quite recently I discovered that I like mentoring younger students and teaching those, who are interesting in math / programming. I spent some of my time by organizing an annual international math competition for high-school students and participating in a lot of various programming contests myself.
New members are usually interested in advanced algorithms and techniques. I would recommend them to start practicing on much easier problems and once they master them, they can proceed further. You need to write a lot of code and remember “Practice makes perfect”!
I first heard about Topcoder from my friend Delsius, who was a Charles University student by that time. I was always rather interested in the Algorithm track, and participated in quite a few MMs, only because they are not much different and you can use similar kind of skills. It was always my dream to advance to the finals, but I never thought I was going to achieve that by Marathon track!