The phrase "gradually create" is correct and usable in written English.
You can use it when referring to creating something over a period of time. For example: I gradually created a new website for my business over the course of several months.
Angola needs "well-structured, well-designed programs, meaning programs that will gradually create wealth".
We mean to gradually create a guide to the vast archipelago of independent-press poetry publishing.
They might be painful, but they might not kill the dreams, and they will establish something that by its own presence will gradually create an incentive not to go back to violence".
Back in 1979 it was a perfectly logical idea to suppose that direct elections to the European parliament would gradually create Europe-wide parties, politics, media and eventually a European demos.
Also, in some cases, gas flowing to the center of a disk galaxy could gradually create a "pseudo bulge," as opposed to a primordial bulge, where a black hole could accumulate mass.
Water seeping through soils into the bedrock, water collected by sinkholes, and surface streams sinking underground at the margins of karst areas all percolate along fractures in the bedrock and gradually create sizable passages by chemical action.
And however compressed and difficult this exhibition is, it gradually creates an effect.
From Adams, Martland found a belief in his own music and gradually created his own post-minimal urban soundworld.
As that weariness gradually created a space between them, Pintor filled it with cruel, stiff-armed hooks.
In the southern part of the Qi state an extensive perimeter wall was gradually created using existing river dikes, newly constructed bulwarks, and areas of impassable mountain terrain.
In this capacity he gradually created a state medical department to administer public health, establish state scientific research, perfect the vaccination system, and supervise the medical profession.
