It all depends on how strong you like your tea. Most brand teas, Like Yorkshire Gold, Liptons, PG Tips, Tetley, are blended indian teas.

Earl Grey tea is an indian tea flavoured with bergamot oil (I can't abide it myself).

Straight indian teas will brew quicker and stronger than 'china' teas. Broken leaves (as you get in most tea bags) will brew even faster. For a lighter taste with a full flavour get unbroken tea. The difference is, while I would leave unbroken leaves in the pot to brew for a few minutes, I wouldn't do that with broken leaves and definitely not with tea bags.

Not all tea tastes good with milk in. The 'china' teas (like Kemun) will mostly taste better without milk. Others taste awful with milk in - Lapsangsuchong, jasmine, or japanese green teas.

My personal favourites -
Tea bags - PG Tips
Loose broken tea - Twinings 'All Day' tea
Unbroken tea - Orange Peko (will take milk) and Jasmine.

Personally, I don't hold with tea infusers, other than in emergencies (they're a reall bind to clean out for a start). I'd go for one of these options....

6 Cup teapot

You can get 2 cup versions of these. They work really well as you can lift the tea out completely once you've acheived the strength you desire.

Or Tea For One