With reference to the creation of a design template for marketing materials I have the following questions. My intent is to convey and image of professionalism, knowledge and friendliness
1. What kinds of design themes would you recommend across all of the materials like brochures, business cards that would support this image. For example should I use circles, squares, lines, bars etc
2. What kinds of symbols, shapes or other graphic design elements would be best to add to the template to convey this image.
It sounds like you need to hire a graphic designer - creating a template for marketing materials requires brand and design expertise. This holds even more true as you are seeking "professionalism" to be conveyed in your final design. If you are not a designer (and from your questions, I can guess you are not), you are risking looking unprofessional taking this in to your own hands.
There are no pat design-theme formulas or shapes that can be assigned (or that have inherent meaning) without knowing about your brand, your customers, products, and more. A good designer will take some time to understand what you need and develop the right solution custom to you in the context of your business goals and brand objectives. Good designers have spent years in school, then many years after honing their skills in visual hierarchy, tone, balance, typography, color theory, visual communication, branding and much more.
If hiring a designer is out of the question, I suggest that you take a look at your existing brand (visually, what do you have? logo, tag line, website), and then create something as simple as possible for your template using minimal elements. Stick only to the colors and typefaces of your logo, or fewer if there are more than 2. Keep it consistent across ALL materials, and refrain from making your logo too big. If you don't have a logo or anything already developed, then all the more reason to keep it simple with a type treatment of your business name in one color. But again, if your aim is to be professional - then get professional design done by a real graphic designer. Many designers can find a way to work within small budgets, within reason, of course. If you are serious about your business, you should think of hiring a designer as a sound business investment. If your brand and branded materials look shoddy and unprofessional, that is likely how you will be perceived.