I wouldn't recommend using AW express because you lose most control over the account. There's no telling where your ads will show up because you don't control the bids, can't effectively manage keywords, and can't modify the settings appropriately on campaigns to really focus on ads. I've always said AW express is like playing blackjack, but letting the dealer decide your hand for your. Adwords is the primary revenue stream for Google's business, so they're not in it to make you the best ROI but to keep you happy enough to keep spending money with them. Increasing the monthly spend won't help your ads move up, the only way to do that is optimize the campaign. It's not just if you bid more you'll show higher. It all depends on quality score for the keywords used. If they're broad match with low quality score, then a competitor can theoretically bid lower than you to achieve a higher position if their keyword has a better QS. You will really never know what's going wrong or how to fix your campaign if you use AW express.
My advice is to ditch AW express and actually manage your campaigns. If you don't have the time to learn, then hire someone who already knows it.