That's not a bad start at all, Member #1. Call me Captain Obvious but of course you need to get the book first.
1) Characters: Fine as they are. You can field a General and BSB on horses (get them ward saves if you can and/or the charmed shield for one), a L4 + complementary wiz if you like OR 2* L2's. You can also use a WP model as an Archlector if you want. You might want to buy an Engineer at a later date since he improves the Hellblaster considerably or a BSB/General on foot if you chance upon many cannon but that's really optional. No acute need to spend any money here.
2) Core troops: Halberdiers have long been considered the optimal choice, and they probably are but especially Spearmen aren't that bad. I suggest that you either convert your Spears/Swords/some of them to Halbs and build the rest as such as well OR that you try to get a decently sized unit of Spears going (40-50). With two unopened boxes, 38 + two characters is a start.
To support them, you can use detachments of Swordsmen, handgunners and/or Free Company. Swordsmen and Free Company are both a little too expensive for what they do, pointswise, but especially the former serve well as detachments whose job it is to survive for as long as possible.
My suggestion would be to use 1-2 combat detachments and field the handgunners in a separate unit so that they don't slow you down with move or fire. Of course, handgunners are not that effective, so a small unit to clear chaff is really all you need.
Knights are core (regulars or Inner Circle) or special (Reiksguard), so give you a lot of flexibility. You can field small units of stubborn Reiksguard or plain vanilla core knights, a large unit of RG or Inner Circle. The latter would probably be the best option short- to mid-term as it helps fill your core requirements and adds some punch and mobility.
Another box or two of State Troops never hurts but that's about all you'd need in the short term.
3) Special and Rare look good. The Mortar isn't very useful but two cannon are often a staple and both Hellblaster and STank are excellent choices. No need to spend any money here. Things that are nice to have are the new stuff: A Hurricanium or Luminark (I hear the top can be swapped out, so buying one would be sufficient to at least test out what you like better) and/or a box of Demigryphs to add some punch in combat.