Should you buy the new 32 slot WvW and PvP bags? 

as long as the supreme runes of holding are more then 10 gold, i really wont bother with the bags...we really need more sources for those

It's worth noting: The pve mats can be farmed in 1-2 days, while the wvw equivalent can take months of farming the currencies

The ideal inventory size is + 255. That way you can open and salvage entire 250 stacks of unidentified gear in two selections. The extra 5 slots are just buffer.

The other benefit is that you don't need to level any crafts to get the new bags. We still need another source for supreme runes of holding- maybe the vault.

But be careful you need those grandmaster mark shards for leg armor crafting. Wasting 20 to go from 20 to 24 isn't worth unless u have loads of shards

You should probably have mentioned the option to convert gold into gems and buy an additional bag slot for your character to use with a normal 20-slot bag. I am currently not playing so I can't compare prices, but still: Assuming you've got every slot equipped with those, upgrading one of them to a 32 bag provides you with 12 more bag space. Instead getting another bag slot and a 20 bag obviously yields 20 more bag space and a slot that you can possibly even upgrade further down rhe line. So you'd need to compare the cost of one bag slot plus one 20-slot bag to the cost of one 32-slot bag. The former would have to be almost 50% more expensive than the latter for the value per slot to be close to _equal_ (dismissing the utility of upgrading the new slot one later). Maybe someone can look at gold to gem exchange rates and do the math. It would not surprise me at all if getting a new bag slot plus bag by converting to gems would be significantly cheaper than crafting one single bag through the means provided in-game. That would be such a classic ANet thing. (This obviously only works as if you're not maxed out on bag slots yet...)

superior rune of holding is 10g each so, idk if thats something

I have overflow of 18 slot bags form wvw .... can i use them somehow?

It's only worth it if you already finished your legendary armors and have extra grandmaster marks lying around.

you paid 250 ectos and 100 gold and got 450 ectos and 25 gold. pretty sure you broke pretty even.