I take it you're looking for something to get you through the long haul to 31, correct? I have a few ideas that could be a good idea going through for a gen, all of them can be cheap.
Hoplite: Ram your spear into people from a distance, cower behind a shield. Since you're strapped for cash all you really need is a decent shield + lengthy spear of choice. I'd suggest the Hypaspist build from Ronin's Hoplite guide, strength builds benefit low budget builds as you typically get more 'bang for your buck'. Here's the guide to look at with build: http://forum.c-rpg.net/index.php/topic,34674.0.html
Cavalry: I know what you're thinking, but cavalry isn't expensive when you use budget gear. Not only that but it's incredibly satisfying to ride by and blast somebody with a ride-by attack in superior equipment! Pretty much you have two routes to go with cavalry on a budget, lancer or swinger. The lancer specializes in quick hit-and-run backstabbing and getting the fuck out, whereas the swinging cavalry supports infantry and harries cavalry off of them. (I'm personally playing 2H cav and it's a blast.) Gear I would limit to just a Rouncey and weapon of choice, with a little low-tier armor to pad the instant death on horse.
Any of these three builds I would suggest, note they also have full athletics. These are not dedicated horseman builds and will work from horseback as well as your run of the mill infantryman.
Lancer Strength: 18
Agility: 21
Hit points: 61
Skills to attributes: 8
Ironflesh: 4
Power Strike: 6
Shield: 0
Athletics: 6
Riding: 7
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 0
One Handed: 1
Two Handed: 1
Polearm: 114
Archery: 1
Crossbow: 1
Throwing: 1
One-handed Level 30 (4 420 577 xp)
Strength: 21
Agility: 15
Hit points: 70
Skills to attributes: 2
Ironflesh: 7
Power Strike: 7
Shield: 5
Athletics: 5
Riding: 5
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 0
One Handed: 114
Two Handed: 1
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1
Level 30 (4 420 577 xp)
Strength: 24
Agility: 15
Hit points: 69
Skills to attributes: 8
Ironflesh: 5
Power Strike: 8
Shield: 0
Athletics: 5
Riding: 5
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 0
One Handed: 1
Two Handed: 114
Polearm: 1
Archery: 1
Crossbow: 1
Throwing: 1
Pikeman/Longspear-man: Ram your lengthy stick of doom into your enemies, strike fear into cavalry as they approach the infantry blob. Be an overall terror in teamfights, players will actively seek you to kill you because of your value in battle. This build is probably the most economic but also the most difficult, as it will require a great amount of skill and assistance from your teammates to be effective. This build is effective and fun and cheap if you can make it work.
I would suggest two builds, the first is a hard hitting SOB that will rack up a fair amount of kills. The second is a speedy support fighter that can consistently harass and ram his long stick of doom into the heads of his foes.
Strength spearman.
Strength: 30
Agility: 12
Hit points: 71
Skills to attributes: 14
Ironflesh: 3
Power Strike: 10
Shield: 0
Athletics: 4
Riding: 0
Horse Archery: 0
Power Draw: 0
Power Throw: 0
Weapon Master: 0
One Handed: 1
Two Handed: 1
Polearm: 114
Archery: 1
Crossbow: 1
Throwing: 1
Diggles' very own GUGNIR SPEARMAN build. Credit to the NH clan thread: http://forum.c-rpg.net/index.php/topic,12329.0.html
Strength: 15
Agility: 21
Hit points: 60
Skills to attributes: 2
Ironflesh: 5
Power Strike: 5
Shield: 5
Athletics: 7
Weapon Master: 7
Polearm: 164