Twitter marketing requires a lot of content, that's how you'll be able to reach more people. I get a lot of traffic on twitter when I post at least 3 or 4 times a day, this helps me reach a lot of people in different time zones. This works well if you have a blog/youtube channel and a lot of content.
You can play around with your posts and post the same thing you posted last week Tuesday in the morning and post it next Wednesday in the evening, for instance.
Twitter is not like other social networks, with facebook you can post once a day and still get a lot of people to see your post because they use an algorithm. People on Google+ will mostly see your posts even if you post once a day simply because there's not a lot of people to follow on G+ so most people won't need to scroll deep in their newsfeed to see your posts.
But Twitter is different because there's a lot of people to follow and the newsfeed gets cluttered pretty quickly so you have a better chance of reaching people if you post at least 3 or 4 times a day.
All social networks have bots, but that shouldn't stop you from using social sites. However, you can use a tool like managefilter.com to get rid of all spam account, inactive accounts and bots.