You ought to concentrate on one tech type at a time, both trade and production tech adds to your income and so the next tech you research will arrive more quickly for each finished level (they may also unlock abilities (like getting a monopoly) and buildings (like workshops) that increase your income).
Government tech adds ideas and buildings that may also achieve this at certain levels.
Therefore it's more efficient to concentrate on one tech at a time (you'll get that tech a lot more quickly and then it will increase the speed for the next tech you research).