More Ads or a Better Store?
Before raising the budget, follow the money through one order. Return on ad spend tells you little about what's left after product costs, shipping and returns.
Example: 1,000 paid visits
These figures are fictional. At €0.60 a visit, 1,000 visits cost €600. With a 2% order rate, that's 20 orders. If each order contributes €30 after variable costs but before ads, you have €600 before advertising. Subtract the €600 media spend and you're at €0 before fixed costs.
Double the budget at the same rates and you double both orders and costs. The result stays €0. In practice, the additional clicks might cost more or bring a less suitable audience.
What might a store improvement be worth?
At 2.5% rather than 2%, the same 1,000 visitors place 25 orders. That's 25 × €30 minus €600, or €150 before fixed costs and the cost of the store change. Those five extra orders are an assumption. You'd still need evidence that the change delivers them.
Where I would look first
If the audience is wrong, check search terms, creative and feeds. If the right people arrive but can't find a delivery date or understand the price, look at the product page. If shop orders and ad reporting don't agree, check measurement first.
The findings might point to Google Ads, Meta Ads or conversion optimization.