I guess in ur budget u can easily get civic 96-98 under 550k with suitable body and weak engine
i reckon mod should be descent,emphasize more on mechanical stuff such as brakes,suspension,Intake, exhaust, headers, spark plugs and wires.
Engine:Swap it with d16(DOCH) or k20a
Body:add new lights and paint job should be done from some one renowned,add spoiler,extenders e.t.c,add low profile tyres with descent RIMS
Interior:Sporty seats,Digital meter,slight garnish to Dashboard
and finally s good sound system.