which subject i want to take for marketing asstiant?please guide my career

Marketing! I work with several marketing assistants in my company and they all studied marketing in college. Go for it!

You could get into marketing with various levels of experience. Many marketing executives enter the job with an HNC/HND or degree. Previous experience is very highly valued and may allow you to enter without a degree.
Relevant degree subjects include:
marketing
communications
advertising
business and management
psychology.
To do a degree, you will usually need five GCSEs (A-C) including maths and English, plus three A levels. You should check with universities for exact entry requirements as other qualifications may also be accepted. See the UCAS website for more information about degree courses. (www.ucas.com)

A degree is not always essential if you have business and marketing skills. You may get these through jobs such as sales, customer service or public relations work. Voluntary work would also be a good way for you to get experience. You could also join a company’s marketing department as an administrator or assistant. This could give you enough experience to then work your way up to become a marketing executive.
- See more at: https://nationalcareersservice.direct.gov.uk/advice/planning/jobprofiles/Pages/marketingexecutive.aspx#sthash.IPO3XDkn.dpuf

As a marketing manager, you will typically be responsible for planing, directing, and coordinating marketing policies, as well as developing and implementing pricing strategies for your company or outside clients.

Economics, Business and Finance Studies, and Computer Science are subjects that you should consider if you aim to be a marketing manager.

Take relevant high school courses. If you think a career in marketing management might be right for you, it's best to take relevant courses as early as possible. This will help you determine if you have a lasting interest in marketing.

Apply to college programs. You will need a minimum of a bachelor's degree to become a marketing manager. Some colleges have an actual bachelor's degree in marketing management, while others offer related degree paths like marketing, business, business law, and communications.

Join an interest club or attend seminars. Some schools (especially larger universities) host school-wide interest clubs. These can be an excellent way to make connections, learn more about your chosen field, and build your resume with additional experience.

Get an internship. Some employers consider internships a requirement for any applicant hoping to become a marketing manager.[9] Many of these internships offer hands-on experience working at real companies and firms to learn how the business works and what a career in marketing management will look like for graduates.

Graduate with a bachelor degree. Once you've completed your coursework and gained some extra-curricular experience (including clubs or honor societies and a hands-on internship), you'll graduate with a bachelor's degree in your chosen field. You'll need to have high grades in all of your coursework if you plan on attending a master's program, so make sure you apply yourself completely during your collegiate studies.

Consider attending graduate school. Some employers may require that you have a master's degree or professional degree. Others may simply require a well-rounded undergraduate education with a lot of hands-on experience. The best way to determine whether you'll need to advance to graduate school is by researching your dream companies and seeing what their requirements are.

If your dream job requires an advanced degree, or if you believe that an advanced degree will open up additional career opportunities for you, you may want to consider applying to graduate school.
Talk to professors you worked well with in your undergraduate studies to see if grad school may be right for you.
Search online for accredited graduate school programs that focus on marketing, business administration, or business management.

Take business classes, and talk to the instructors about directing into which classes to take once you got the basics down. You could take the lower division classes at your local community college to save on cost, and then transfer to a university and finish with a bachelor's degree in marketing.