As you say the price dpends on what you want doing and also how quickly you want it doing. When we moved into our present place (some 20yrs a go) the garden was also in a hell of a mess as well as slopng quite steeply, over the next 10 yrs we built retaining walls terraced it, put in a pond, decking, patios, rockeries and borders, doing it bit by bit as time, the weather and money permitted. luckily most of the top soil was just redisributed and what rubbish I had to get rid off I could do at work but even so I would estimate that over the years we spent �7-10,000 for material, but as I said we did virtually all the labour ourselfs. As to some costs I know skips for instance can cost from about �75-�150 depending on size, but it's that long since we had to buy any thing other then bedding plants I couldn't really say what the sort of materials you'd need would cost