One thing you may want to think about is designing into the circuit what is called "keep-warm" or "soft-start". When using regular incandescent lamps, there is a large inrush current while the filiament is cold, this can produce very large short term current draws. Especially when many lamps are turning on at the same time. This does 2 things, one, it is hard on the lamp and shortens its life, and two, it can produce alot of electrical noise that Triacs are not going to like, causing dv/dt false triggering that Sebi mentioned.
Often lamps in this type of arrangement are constantly powered at a very low level, just enough to keep the filiament "warm". This stops the mechanical shock to the filiament when the lamp is powered, and greatly reduces the inrush current of a cold filiament.
Sometimes, depending on the lamps used, or the flash rate, the lamps filiament does this on its own if it is flashing fast enough to never really cool off.
All of the lamp driver circuits I use at work include a keep-warm and soft start design by way of PWM ( Pulse Width Modulation ). Since the stuff I do involves DC, the circuits are not of much use to you, but the same principles apply to AC lighting.
There are many circuits available for doing what you want, and at the risk of getting the Trout Slap for posting a link for another site :lol: when there are likely some here, here you are:
https://www.epanorama.net/documents/lights/lightdimmer.html
this link has some good basic info, and explains triacs, keep warm, etc