Spirulina is very good! I prefer a mixture of many sea plants, but your picking out one of the better ones and expensive ones, I suggest you buy it by the pound, much cheaper!
The sit ups are OK if your feeling great and want to build some muscles in certain areas. I personally do not do anything special like exercises. I prefer what i call a leg shaker, better known as chi machines, you do nothing but relax, the machine does the job and the best. My second best method is the up-side down inversion machines. These 2 devices take zero effort and do the most. Exercises are ok, but I prefer the body be acid free as possible and few are, so I don't suggest exercises other than the 2 mentioned.