You will never know if your spells will work or not unless you throw caution to the wind and give them a go. Magic as with anything gets better with practise. It is likely that you will get a few of your early spells wrong and not achieve very good results but over time you will get better. Think of it as being a bit like me saying I’d like to paint a masterpiece but I’m worried that if I have a go my painting might not be very good. Realistically my first efforts are going to be pretty rubbish but my only chance at painting the masterpiece lies in me being willing to pick up the paint brush and have a go.
Yes I do cast spells and yes they work. The reason I know they work is that I am very specific about what I want to achieve and I have confidence that when I cast I will achieve it. That comes with experience and goes back to the idea of practise. Magic works with the idea of cause and effect through intent. The key to spell work is understanding and focusing that intent. The only way to direct intent is having a good sound understanding of the results you want your spell to manifest in. You know a spell works when you get the results day in and day out that you are directing with your casting.
I’m of the opinion that a spell is only as good as the person working it. I have a personal dislike of using other people’s spells and I honestly believe that half the success of a spell is down to putting in the effort to write it yourself. Most of the sites promoting spells on the internet are rubbish. I can’t say all as I do occasionally come across some gems but they are well hidden within the nonsense. One credible spell reference is The Element Encyclopedia of 1000 spells. Have a look at it. I know a lot of witches consider this a good read. Again, I’d still much prefer to write my own and some of the spells inside the book are a bit silly. But there is some good stuff too. Use it as a starting point.