My advise is ..... don't go PH. Bad experience there.
You can try south east tyre or leong seng. They are much better in
term of service and selection of rims.
Trust me, i have been to all these three before. I even been to YB,
Stamford (both lok yang and loyang), and a few more when sourcing
my rims.
The above mention two leave a greater impression on me, and i
actually change my rims at one of the above mention.
The offset of Lancer should be 40 for 15" rims (195/55/R15). 42
might fit but you got to check.
Prices of rims depends, and Taiwan ones are actually cheaper, such
as Advanti Racing and RM. Lenso are good too, from
Thailand............ Taiwan rims usually ard SGD 110.00 a pc for
15".
More expensive one will be OZ, Enkei, SSW (from stamford) etc
etc..........
Take note of the weight of the rims. Heavy one will tend to slow
down your car a little during pick up.