Ah - clothing has been such an issue for me. I am not vain, and I am not a fashion victim, I just got so frustrated with things not fitting/having to spend money on clothes for such a short period of time - it's been a source of a few hormonal strops I can tell you!! 
ANYWAY....I can recommend a couple of things that will grow well with you:
1 - Maxi dress- could only wear a maxi dress on a good day pre-pregnancy, but wow they are amazing now! I felt much more comfi wearing them when I had a more discernible bump and did not just look chubby. I have a black one which is invaluable - you can dress it up or down and add layers underneath or above - great for work. Flowery and stripey ones all in the sale at the moment - check out New Look and Dorothy Perkins maternity online for some really cheap staples.
2 - Beware of Jeans - with under bump jeans after about 25 weeks the pressure under/on the bump was unbearable. Over the bum Jeans just did not suit me - with a bit of a 'plumper bump' - terrible!
3 - Long vest tops and 3/4 length tops excellent buys, you can layer them and just by buying 3 or 4 of each, they are relatively inexpensive and it does not look as thought you are wearing the same every day.
4 - Yoga/Plazzo pants - currently some nice ones in New Look and I have just purchased some from Mothercare in the sale for £6 - bargain! A black pair of these are fab as you start to get bigger 30 weeks +
5 - pregnancy leggings and floaty tops
6 - flip flops for the fat feet - aaaahhhhhh, comfy
The issue that I had with online is that through much ordering through ebay/online stores about 90% of it didn't fit - even though you are supposed to go for your pre-preg size, I just found that size varied so much, even within brands (apart from Maxi dresses - my size fitted every time) - . So, I would suggest that a shopping trip may be in order, or just be prepared be a bit zen and not to get frustrated when you have to return stuff.
Have to say I am nearly 32 weeks - so can't comment on humongous bump status - but I imagine that the maxi dress will be with me all the way!
Happy pregnancy!
xx