The Human Connection
First of all, I really sympathize with your situation, due to I have already been through that situation and I know how the peers pressure feels and how hard is to keep up with your beliefs and do not succumb to the consumerism.
I absolutely agree that being up to day is very important, due to it allows you to keep in touch with your friends and keep up with the latest trends and new technology. However, it could also be a double-edged sword that can be very useful, but at the same time increases the consumerism. Because, the vast majority of teenagers become addicted to latest gadgets and social networks, due to teenagers feel that they really need them. In this way they only loose contact with real people, because they only live focus on keeping up with trends and they think that they can not live without them.
Thirdly, I think that downloading free applications in your cell phone is a way to keep up without spending too much money and you only need Internet or Wi-fi connection. For instance, if you want to download music, a good application could be Invenio Music. If you want to download an e-book, you can download an e-reader. In addition, if you want to keep up in touch with your friends, you can search a free application and download it.
Finally, I think that currently technology is an important tool that can become you addicted, for that reason you have to learn how to use and handle it. I also think that there are more important things in life to have the latest gadgets. For example, if you save money you can buy a present for you mother's birthay, you can go to a cinema or a concert with your friends or save money for what you really think is important and necessary for you. Do not let that your peeers pressure changes your beliefs, personality or lifestyle.
I hope this helps with your problem.