You must be careful when purchasing traffic since a lot of places/sellers are just selling useless bot traffic.
After looking at your Twitter page I have 3 recommendations.
1. Use hashtags in your Tweets. This helps to get your Tweets found in Twitter's search better. I thought they were BS, but after some testing I have found that they really make a difference. Just don't get carried away.
2. Send out some Tweets with some links to good articles, stories, blog posts that are related to topics that your target audience might be interested in. It can help draw them to your Twitter page, read your Tweets and hopefully visit and sign-up on your site.
3. Include pictures/images in your Tweets if possible that are related to what the Tweet is about.