I am currently a Junior and the school year is just starting for me. My current unweighted GPA is a 3.05 and I want to raise GPA to a 3.5 or a 3.6 by the end of this school year. Is that possible? I understand every school has different weighing options but is that doable?
Only you know how your school calculates GPA and what classes/credits you have. Anyone shooting for a 3.5 ought to be able to do their own math to figure this out. 
^^^^This. Also, only use core classes to calculate your unweighted GPA. Assuming you have 10 core classes so far, and you are taking 5 this year, even with straight A’s you would not be able to get to a 3.5/3.6 unweighted GPA. But, you can figure this out based on your actual number of core classes over 3 years. Weighted GPA calcs will obviously be different, and based on your school’s grading policy/chart.
Whether you can or not, you can raise your GPA somewhat and that is a good thing. The better you do in harder classes, the more colleges think you can do college level work.
. Here are ideas
http://talk.collegeconfidential.com/high-school-life/2026961-what-to-do-when-you-arent-doing-well-in-a-hs-class-p1.html
Let’s say that you took 6 classes per semester in 9th and 10th grades, so you have 24 grades (6 x 2 semesters x 2 years). We will pretend that you got 23 B’s and 1 A to arrive at your 3.05. An A is worth 4, a B is 3 and so on. 23x3 plus 4 is 73. So that’s 73 / 24 = 3.05-ish. If you take 6 more classes in 11th grade and get all A’s, your GPA would be calculated as 121 / 36 = 3.36. So no, you wouldn’t be able to get to 3.5 unweighted. Maybe weighted, if you took a ton of AP classes.