you are not going to really buy petros at the moment.
there are still no petros, blockchain or transactions.
That's very interesting! So Maduro basically pulled the 9837563 gazillion dollars number out of thin air? With no blockchain, no auditable contracts, and no recognizable party announcing how much they're investing, can we really trust what Maduro is saying? I think not.
Yes, you can trust Maduro. But Maduro is a chief of State, not a technician. So you should listen his generic declarations about the project, don't expect specific technical details.
He declared that investors offered more than 750 millions dollars in 24h from the pre-sale launch, which is quite possible since they're offering 40% discount on the oil price. The initial investments in Petro will be much higher than that, likely.
You can make an offer saying how much Petro would you like to buy on the official pre-sale page (after registration):
https://regpetro.mppeuct.gob.ve/