I've been using Ebay Elevate since July last year. I don't know about any alternatives, but I can vouch for them. The course is a certain amount on their website, but if someone refers you, they provide you with a code for a substantial discount. DM me if you decide you want to go with Elevate, and I'll let you know how much the course is with the discount (there are different discount codes so the referrer can make more commission, so it's not fair on people who make their money on referrals if I publish what the course will be on the best discount code for all to see, but I'll let anyone know privately. Hope that makes sense!).
I've made nearly £4,000 since I started in July. It could have been a lot more than this (my best month was £1,260 profit), but because I have other self employed earnings and the profit margins are tight, I was concerned about the VAT threshold, so I haven't been expanding my store like I could have done. It's one of these things where the more time you put in, the more you will make. I haven't put a lot of time in for that 4k. Some are making huge amounts but to be honest, I'm not sure how profitable it would be if you hit the VAT threshold (and it would be very time consuming getting all of the VAT invoices...), so that's something to bear in mind if you go down this route.
Hope that helps. If you have any questions give me a shout.