To determine Emeka's total gain or loss, we need to calculate the total cost and total revenue.
The total cost of buying 50 machines at a cost of 1000 each is 50 * 1000 = <<50*1000=50000>>50000.
Emeka sold one-tenth of the machines, which is 1/10 * 50 = <<1/10*50=5>>5 machines.
He sold these 5 machines at 1500 each, so his revenue from these sales is 5 * 1500 = <<5*1500=7500>>7500.
The remainder of the machines is 50 - 5 = <<50-5=45>>45 machines.
Emeka sold these 45 machines at 1050 each, so his revenue from these sales is 45 * 1050 = <<45*1050=47250>>47250.
His total revenue is 7500 + 47250 = <<7500+47250=54750>>54750.
To calculate the gain or loss, we subtract the total cost from the total revenue.
Gain/Loss = Total Revenue - Total Cost
Gain/Loss = 54750 - 50000 = <<54750-50000=4750>>4750.
Emeka's total gain is 4750.