Debreu is certainly a superb exposition, but I think a better choice is McKenzie, for two reasons:
Debreu's model assumes a fixed number of firms, which means that it's implicitly a model only of short-run equilibrium. McKenzie's model (which was contemporaneous with Debreu's) allows the number of firms to vary (at the cost of assuming constant returns to scale) and is therefore a better introduction to the kind of models you seem to be interested in.
Debreu's book, well written as it is, dates from the 1950s. Because McKenzie's book is much more recent, it's able to offer some historical perspective that I think will be helpful to you, as well as incorporating a lot of material (e.g. uncertainty) that wasn't well worked out until more recently.
Like Debreu, McKenzie was a good and careful expositor.