Hi there. I'm a beginner in this SBG, currently playing some skirmishes using a friend's miniatures. I was looking at the different armies looking for the one to use, and i stumbled upon a small Harad warriors lot (28 models, warriors only, some with spears some with bows) and i was looking at the stats and rules...
I've read around that they're not bad, but i can't see how they should work, being paper thin compared to things like uruk-hai and even just an esterling warrior with a pike, in scenarios where you often start too close to the enemy to have archery have a positive effect on the battle... (we're using the scenarios in the Hobbit book)
Can someone explain to me how to get the most out of the Harad faction, and if it's worth to buy these 28 models considering i won't be able to get Serpent Guard/Rider or other Harad models? (can't find them anywhere, i'd have to convert them, if that's possible)

They're not terrible - even for the basic troops. They're cheap, so you can get a lot of them, and the bow limit for Harad is 50%, not 33% so you can get a lot of bows. Upgrade the archers to Warriors of Karna, and they have a shoot of 3+ and get to re-roll 1's to wound (poison arrows), which is pretty good.

Their cavalry is cheap as well, and have bows and war spears (lances), so pretty solid.

Their major drawback is low defense, so expect them to die once the lines clash. Try to stay away and use bowfire to maximum effect.

They are better when you can add some of the specialty troops and better heroes.

Abrakhan Guard and Warriors of Karna make for better combat troops than basic Haradrim Warriors. Corsairs offer some desirable troops.

The Golden King is outstanding as a leader. The basic King, chieftains are pretty solid for their cost.

Pros: Decent variety, good shooting, decent (not great) light cavalry (hence mobility), relatively low cost troops, good archery and poison re-rolls. Access to 2 wraiths as well. A number of the basic troops are available as plastics, so they're not highly expensive to build a basic force, although the specialty troops can get more pricey.

Cons: Low defense across the board, hence fairly low durability.

Harad is an awesome force. Who else has a mumak? They are soft, but their 50% bow limit is awesome. The golden king can make the dautiest hero run away, hasharin have an effective killing power, watchers of Karna are the best unit in game (price versus pay out), lots of spears and skirmish based cavalry. I love Harad forces, they offer so much versatility and are fun to play.