You're twenty eight so you are still young enough for trendy but not so much so that you should go overboard. It would also help if you post your size since some stores vary with size. The only two mentioned here that I personally would shop at are pinupgirlclothing.com and Macys
I would also be cautious about trying to dress "sexy". You can be well dressed and be sexy at the same time. Like if you show cleavage, do not wear a short fitted skirt for example. Also, if you can shop in person and try everything on, even more than one size of something it is better. Check online for what stores are selling now and use it as a guide
Things like stripes and animal print are trending down- they are going to be over. For fall it is going to be a lot of dark taupe, gray, black with jewel tones like ocean, berry, jade, orange(dark). This is great news for plus size women because black is great for a base
Spanx are your friend, get as many as you can when they are on sale or buy similar fitting things. If you have a waist, belt everything, it will give you more of a shape. Also, when you accessorize, pick one statement piece like a bold necklace since you are smaller breasted and keep earrings simple
I am bouncing between sixteen and eighteen depending on the label(better labels have smaller fit). I shop at the following stores(sales for the expensive ones)- Old Navy/Gap/Banana for basic things; forever 21 plus for statement pieces leggings, and tanks(five bucks); pinupgirlclothing.com for pencil skirts, dresses, sweaters; Macys/Bloomingdales/Nordstrom for collection things that I will keep; torrid.com only for boots; I also love these sale stores- Off Fifth/Nordstrom Off The Rack/Century 21 stores like that where you will find something amazing at a great price but it is hit or miss and you have to be selective(I have more stores that I like and accessory labels I love but I can not share everything)
The items from torrid and every other similar store come from the same private label companies. Torrid marks the price up significantly. The quality is terrible for what you buy
It is about finding what is best for your fit while being fashionable. You want to what we call, mix high and low- classic things you might already have with trendy pieces(one trend per outfit). It is not only what you wear but how you wear it- make sure the fit is good, your accessories work with your outfit, your makeup is neat if minimal, your bag and shoes work, and that your hair is cohesive with what you wear
Getting away from lane bryant will be the best thing you can do because the fit is very boxy