Lol not looking for a gym alternative lmao I know I need to get more active
The best metabolism boost, from the research I have done, is not "gym" exercise, but actually incorporating more standing and walking for longer periods throughout the day.
So simple things like parking at the end of a parking lot, and standing while on the phone instead of sitting, or even watching TV or using the computer while standing up, really boost metabolism in a way that 30 minutes of jogging or weight lifting a day can't reach (of course those activities are also good, just in a different way).
The general recommendation is that you should aim for 3 hours or less of sitting per day.
There is evidence that the glycemic load of your diet can contribute to your metabolic rate (http://jama.jamanetwork.com/article.aspx?articleid=1199154). Lower glycemic diets contributing to a faster metabolism than higher glycemic diets (or at least less decrease in resting energy expendeture rate following weight loss). I believe the study found a difference between low-glycemic (not low carb) and low-fat diets that amounted to about 125 calories burned per day while at rest. The study was done with "overweight and obese young adults" so I don't know how well those numbers would transfer to other demographics.
The really low glycemic or non glycemic foods would be like oil, peanut butter, nuts, seeds, tofu, meat replacements, seitan... High would be sugar, white rice, pasta, bagels, boxed breakfast cereals, agave, raisins, dates, etc. Beans, lentils, whole wheat bread, whole wheat pasta, fresh fruit, soymilk and so on are moderately low.