How about spearman? I have like 1B So if I'll do a spearman he will be stronger then a mage because str and dex is cheaper then INT and M.Att so I can buy more powerfull equipment
Not necesarily. Mages are very different from spearman. Either class will take wayyy more than 1bil to make strong. Mages are considerably easier to play without a lot of funding though due to their mobbing skills. For example I made a bishop and sell leech to fund my slightly expensive Dark Knight. I would make a mage and then fund your main character. Unless you want the mage to be haha.
Even an unfunded mage can train WAY faster than a spearman. Look in the post about % per hour But my advice would be to play any class you like. If you like spearman training and bossing, just go for it. What is important here is what is fun for you