Most of my orcs and goblins are originally from the Games Workshop LOTR skirmish game.  Called "Middle Earth Strategy Battle Game", I believe.  Their orcs are very good, but many other manufacturers also produce good Orc figures. Oathmark is one example.  Ral Partha did some beautiful orcs forty years or more ago; sometimes they are still available on ebay.  GW (MESBG) “goblins” are quite a bit smaller; they work well for Rabble stand mixed in with a few larger figures.

The other Games Workshop system, Warhammer, is entirely too florid, too exaggerated and cartoonish, with outsize weapons and expressions and much too large, to be appropriate for Tolkien's Middle Earth.

A moment to comment about "Orcs" and "Goblins" in Tolkien.  Tolkien uses the terms “goblins” and “orcs” interchangeably, with “uruks” or “uruk-hai” as a term for larger, near man-sized members of the same race.  They are not different species.  The term orc sometimes implies a larger being than a goblin, but they are both the same type of being.

Please don’t paint them green.  In Tolkein they are described as “swarthy”, or “sallow”, or in many ways – but never as green.

For Trolls and Hill Giants there are many appropriate figures; one source is Vendel Miniatures, which has a Hill Giant that I'm quite partial to.  The Games Workshop MESBG trolls are very nice, although I would restrict the armored versions to armies under the control of Sauron (i.e., not Wilderland Goblins).