With such light colored natural hair, I can see why you turned orange with henna. A henna gloss would use much less henna and it would be very diluted. I'm talking about getting just a whisper of color.
There is no such thing as brown henna. If someone tries to sell you anything other than red, it is either a commercial dye or a different plant dye (like indigo or buxus, or cassia for clear/yellow).
Henna quality matters a lot. Old henna won't have much dyeing power, and stuff on Indian store shelves is generally old and from a dubious supplier. I only buy my henna from a reputable seller who imports directly and sells large quantities. Mehandi.com is an excellent seller. You would buy a package of henna (comes in 100 gram packs), and what I would do if I were you is mix the whole thing up with lemon juice, adding the liquid slowly until it's about the consistency of yogurt. This is called henna paste. Use a non-metallic bowl and spoon. Cover and allow the paste to dye release for a few hours (dye release happens when you see a sheen of red liquid on the top...can happen immediately or take up to 12 hours...it really depends on the temp of the room, so keep an eye on it), then divide up into small portions, wrap tightly, and freeze (henna stays active frozen for many months). When you're ready to use the paste, just defrost by leaving out on the counter for an hour or two...don't use a microwave (high heat kills henna). To make a gloss, mix a bit of paste (I'd start with a teaspoon of paste) with conditioner and apply to hair, being sure to get deep to the roots. Cover hair with a plastic grocery bag or saran wrap and leave on for the allotted time...start with 30 minutes. Rinse thoroughly and enjoy. Start VERY slow and build up in time/amount if you want more color.
Since a henna gloss is so easy to do, it's easy to refresh the color every couple weeks, so you never have "roots".
Mehandi sells several different types of henna. I would suggest the Henna for African Hair for you as a moderate-level henna. Since you're a natural blonde, you don't need a high dye-content henna, but you don't want a really weak one either. And the African Hair henna is super sifted so it's ultra fine, so it is gentle for rinse out.
Mehandi.com henna for hair: best customer support, lower prices, widest selection
Anywhoodle...that's what *I* would do if I were you and wanted to just add a little "life" back into fading hair.