Improvisation skill is essential skill for musician during praise and worship. Musician always improvise during “free” worship period and with the flow of holy spirit.
Simple improvisation can be create by holding the I note (lets say we use C key then C would be the I note) and play rhythmatically on other note which belongs to it particular key scale. Always a simple sound nice add notes would be around VI note (A) and IX/II note (D).
For example, with repeatively playing I, II, V in appregio mode on your right hand with appropariate chord progression ( try on I, VI, IV, V chord progression or I, III, IV, V ) on your left hand, you will simply get sound nice improvised music feel here.
Of course improvisation is really depending on self creativity and of course with spirit of God you may improvise it with deepest leading people to our God.
God bless