i have the dbxl 2.0 gas, and love it, but i have upgraded it a lot, but from stock there a few things you want to do asap to make it stronger:
Stock shocks are crap! ..were for me anyway, even after a rebuild & stronger springs etc, waste of space, in the end i bought some IRC bigbores, game changer, stock 5T shocks are also a good option that fit straight on i believe.
Aluminium Chassis brace front/rear plus top plate, alloy diff housing if bashing as i believe the stock plastic ones are prone to melting! This will be enough to get you going then just replace with ally if you wish when something breaks. The dibby 2.0 is around £400-500 cheaper than the 5T so by time you do the upgrades it will probably still be a little cheaper than the price of a new 5T, a big chunk of the upgrades is the shocks which are around £200 for a full set of IRC bigbores, so if you can find some use 5T shocks go for them as will be much cheaper prob!
All depends how your going to use it, if your just going to be spinning around car parks/fields etc then there is no need to upgrade big, its only when you start bashing hard you will want to beef up the weak spots.