Check out online growshops, or lighting shops in your area, for 125w enviros, they're really good starter lights, come in blue for veg growth or red for flowering, you can pick em up for under £40 in the UK, under £50 with fittings (no need for a ballast). Normal fluoros don't have the right spectrum for flowering so even if you got more bulbs you'd still end up with weedy bud. If you've only got one plant I wouldn't bother with HPS yet, you could get 2 enviros, one red & 1 blue, for the cost of an HPS, giving you all you need to veg & flower, and HPS aren't great for vegging (plus you get heat removal problems with HPS & humming from the ballast).