Help with postage

[Adie1974_laser]

1. 4Hi all.  I'm new to shopify.  I have been selling on etsy around my disability 

I'm finding setting up is complicated. I've made two listings on one I've manged to do discount for 1 listing buy 3 items 25% off

I'm having trouble with postage.   I've set the boards i engrave to either 90 or 100 g.  I've done uk postage 1st and 2nd la4ge letter 0 to 101g 102 to 250 g then Tracked 251 to 1000 then 1001 to 2000.  

I've tried to test purchase but one item at 90g was showing price for 102 to 250 price (setting at 0 to 100 g didn't work on other boards coming up at higher price so adding 1g worked. 

I've set empty package at 1g 

It's seems hit and miss and not acknowledging postage rates set.  

Not yet fully set up international shipping 

Any help greatly appreciated.  Plus any advice building the store.  Many thanks Adrian