The T-28 is a Soviet tier IV medium tank and the last medium tank on these lines unless you decide to grind to the KV-13.
The T-28 is one of the largest tanks on tier IV and has thin armor so be careful in open areas and close-range engagements.
The 57mm ZiS-4 is a real advantage on this tank. This gun – also found on the T-34 – is accurate, offers good penetration and decent DPM. If you manage to survive, you can do outstanding damage even to tier VI tanks. The T-28 is not good in hiding so you should make sure to stay very far behind. Due to the somewhat good mobility, flanking is also an option. Just be aware of the rather bad gun depression (6°). Most tier IV mediums have at least 10°, if not more. Also watch out for enemy SPGs as they are likely to focus you.
When using the T-28, always keeping an eye on the minimap really pays off. The mobility lets you move around the battlefield quickly and you can retreat from a bad position relatively easily.
The 76 mm L-10 gun and the 10R radio carry over from the T-46, the ZiS-4 from the T-34 and the M37F engine from the BT-7 or the SU-8.
If you haven’t played the T-34 or the BT/SU before, first focus on the gun, then research the engine. After that, go for the suspension and finish with the turret.
The binocular telescope and the gun rammer make sense on the T-28. The binocs extend the already good view range and the rammer helps to maximise the damage output. For the last slot, you could choose between the camo net and the improved ventilation. Ventilation is more useful on a tank that is played agressively and the camo net pays off on a more or less pure sniping tank. It’s up to you to decide.