Some of my students ask me how they can improve their spelling. I have a few tips that can help with spelling but because English is not a phonetic language, spelling is difficult to teach. Rules are only partially helpful. Much more important in terms of spelling, is developing the skills to make connections between the way that words are pronounced and the way that they are spelled. A willingness to refer to a dictionary to check this is essential. In addition, a good memory helps!
Luckily, there are many dictionary apps available which make the process of checking spelling and pronunciation much easier. Each time you come across an interesting new word, try to check a dictionary to find out how it is pronounced.
Don’t assume that words that are spelled the same sound the same! My favourite example of this is that so many of my students pronounce the animal ‘bear’ as though it were ‘beer’, thinking that it rhymes with ‘fear’. It doesn’t!
I suspect the best way to get to grips with English spelling is to do a lot of reading combined with listening. Listening to podcasts whilst reading an accurate transcript is a great way of doing this.
If you want to practise your spelling using text books, it might be worth getting some books designed for school children as these seem to deal with spelling more so than adult language books.
Websites can also be helpful, for example, this link from the British Council is a good starting point.