Spark Gaps

Hi it's Tabraze,

Before I make my first coil I want to get an idea of it in my head. Are
there any tables or formulae that let you calculate how far the 2
electrodes need to be to make the spark gap for transformers of a given
power level?  In static gaps with multiple electrodes how far does the
total gap length need to be? does the size of the gap vary between
transformers of different power ratings? 
I may want to use my coil for special effects when using the skin effect.
Does making the gap smaller increase the frequency?if so does this make the
skin effect more reliable?
Is there any way to find the frequency of a gap if you know the distance
between electrodes, inductance etc?
I don't know if this information will effect your response but you may need
it; I live in the UK, here the line voltage in 230V a.c at 50hz
If there are any tables or formulae then please could you attach them to
your reply or tell me where I can find them?
If there is no such information then I would welcome any suggestions from
experienced coilers.
I know this is asking for a lot but I don't want to spend money on parts
and get it wrong, I'm also very keen on Tesla coils.
Tabraze Malik