An 18 in your casting stat would give you 1 extra 1st lv spell per day, and a 20 would give you 2 extra 1st lv spells per day. Page 17 of the CRB lists how many extra spells you get per day depending on your casting stat. And these extra spells work exactly the same as your normal spell slots.
Ok, just a background I am completely new to spellcasting classes and have no idea what im doing making my cleric but its a blast.
Question is how many spells per day can I cast as a level 1 cleric with 18 score to wisdom. I understand the chart is 1+1 and 30 level spells what is catching me is the extra spells from my ability score how exactly does that work?
As the chart tells you, your 18 entitles you to one extra level 1 spell per day. So your actual spellcasting ability will be 2+1 - you can prepare two spells from the Cleric spell list and one domain spell per day, all at first level.
If you're interested in the formula, it's actually this:
BS(L) = (AM + 4 - L)/4
Where AM is your ability modifier, and BS is the number of bonus spells you get of level L. Always round down (and negative values of BS(L) just mean no bonus spells of that level).
With an 18 Wisdom, you'll get bonus spells of 1st to 4th level. Since you can't currently cast spells at 2nd level or above, you only get the bonus spell slot for 1st level.
So instead of 1+1, you'll have 2+1.
When you gain 2nd-level spells, at cleric level 3, you'll also get the bonus 2nd-level slot. At that point, you'll have 3+1 1st-level spells and 2+1 2nd-level spells.
And so on when you gain 3rd-level spells at cleric level 5, and 4th-level spells at cleric level 7.