It would great if anyone can share the experience whether you have used genomic DNA from cultures, or used cloning technique,s or used g Blocks to make the standard curve for T. gondii
I agree with Dirk Schmidt. To answer your question further, if you already have access to genomic DNA from cultures then you need not buy it again. Simply quantify it using a Nanodrop and dilute it serially (whatever down folds you want) and then run a qPCR to get the standard curve. If you want to know the copy number then you can use online calculators like this one http://cels.uri.edu/gsc/cndna.html
I think this is a good article for q PCR standard curve for Toxoplasma gondii. Please, read this article and gain a better idea of q PCR standard curve study.
Article Real-Time PCR for Quantitative Detection of Toxoplasma gondii