I have a bit of a starter tool kit,keep adding to it slowly with a few essentials this is the next piece of kit I will be adding after reading reviews and advice ,still not decided what one,but will get one ordered by the end of the week
Get whatever cycling-specific one is the cheapest at the time. Within reason obviously. Something like BBB or PRO is perfect. All of them will come with a calibration certificate of sorts.
A cyclist's dilemma is that no affordable torque wrench can handle the range of torques required on a bicycle. This range is unfortunately. It hovers between 3 and 14NM and then with nothing in between, shoots up to 40NM. To make a wrench handle this range is expensive. It is usually cheaper to buy two. However, if you are reasonably competent, you only need one and that in the lower ranges i.e. the BBB, PRO, Parktool etc.
The reason being that mistakes in the lower ranges are dangerous whereas mistakes on the upper ranges that affect BBs and cassette lockrings are not. Further, the BB and cassette can tolerate a huge variance and even a good guess is good enough.
Invest in at least a small wrench. Nowadays you can buy single torque gadgets that are pre-set for 4, 5 or 6NM. Even those would suffice.