Unless you plan on making an army without trukks, which is prefectly possible
A warboss, two units of 20 boyz and a painboy are great start since you can use them in pretty much any kind of army. Hunting down an
AOBR set would be a great options, since you get koptaz on top of that, which are playable in pretty much any kind of army.
After that a unit of
MANz is useful, since you can put them in trukks as
MANz missiles, or have slightly bigger units drive around as hammer unit for a battlewagon rush.
After that, you'll have to decide on some type of army. Bikers are awesome for fast armies but cost too much points for footsloggers or battlewagon rush, mek gunz are great support for kult of speed lists and green tide armies, but you don't have slots to spare for them in battlewagon armies, battlewagons don't work well with footsloggers.