Everyone needs a diet. Does it have to be a fad or complicated diet? Not at all. I think if you are serious about getting fit and starting a diet get in touch with a nutritionist and get the basics out of the way. It can be tough with all the misinformation floating around for someone new to it. If you find your maintenance calories you should be able to figure out a lot of things based on your goals. If you make your diet sufficient in nutritious foods and hit your macros (protein, carbs, and fats) you should be set. This is something a nutritionist can help you figure out.
Also, I really like the pic that Clear posted. If you look at it she looks leaner in the second pic even tough she weighs more. It looks like she added lean body mass and dropped body fat which makes her look leaner even though she weighs more. Your goal should be adding lean body mass by hitting the weights and eating right. So I would get your diet figured out and then get on a structured weight training program.
Good luck!