Realistically - barring a big investment in spend and time - you are not going to make Diamond. We are now in the expensive part of the year for mileage runs (the last two weeks in December meaning there are few cheap fares). Even if you could do mileage runs, 50K is more than two trips around the globe - this is 5+ days of time just in the air alone not even talking about layovers, etc. Even in business we're talking about 3 days+ in the air.
If you are able to manufacture spend and put a bunch of money on Amex cards, in theory you could get two Reserve cards (one personal, one business) and get 60K of MQMs. This would require $120K in manufactured spend in less than two weeks - if you even get the card on time and have expenses to post on time.